bacterial | fungal
| parasitic | atopic or allergic
inhalant dermatitis | food allergies | allergic
contact dermatitis | autoimmune | pemphigus
complex | lupus diseases | erythema
multiforme | neoplastic | endocrine-related
skin disorders | seborrhea | nutritional
Introduction: Skin problems in cats
are a common reason for a visit to a veterinary clinic. This discussion will
review many of the most common skin problems seen in cats. The information will
be divided into infectious, allergic and autoimmune (immune-system related),
neoplastic (cancerous), endocrine (skin problems caused by problems with the
organs that excrete hormones and related substances), and miscellaneous skin
diseases (scaly skin and nutritional skin diseases, etc.).
Infectious Skin Disease
Bacterial Skin Infections:
Introduction: Bacterial skin
infections are commonly grouped under the term "pyoderma," meaning a
skin disease that causes pus. Pyoderma is further broken down into more specific
categories. Cats infrequently experience bacterial pyoderma. There is almost
always an underlying reason for the presence of a bacterial skin infection in
cats; however, this underlying primary cause is not always found.
- Superficial pyoderma: Bacterial skin infections are considered to
be superficial when they are in the outermost layer of skin (the epidermis)
and the hair follicles. Any irritation to the skin can lead to a superficial
bacterial skin infection. Common irritants of the skin include fleas, mange
mites, dermatophytes ("ringworm"), and other external parasites.
Chemicals or toxins, which may be found in common household items such as
hairspray or houseplants, can also cause irritation. These bacterial
infections can also occur anytime the skin is abnormally dry or oily.
Superficial skin infections may suddenly appear as painful, red ulcerations
that ooze clear to cloudy discharge (acute moist dermatitis or "hot
spots") or may progress more gradually as patches of hair loss,
redness, and scale (dandruff).
- Deep pyoderma: Any bacterial infection that involves the lower skin
layer (dermal layer) is referred to as deep pyoderma. These deeper bacterial
skin infections are usually associated with underlying causes instead of
irritants. Causes of deep pyoderma include hormone imbalances (Cushing’s
disease, diabetes mellitus), skin cancers, infection with feline leukemia
virus (FeLV) or feline immunodeficiency virus (FIV), feline acne, repeated
trauma, and foreign bodies such as slivers of wood or fly larvae lodged deep
into skin layers. Some external skin infections, such as dermatophytosis
(ringworm), can also be a cause of deep pyoderma. Repeated self-trauma due
to itchy skin is a common cause of both superficial and deep pyodermas.
Fight wound abscesses are extremely common in cats that venture outdoors or
do not get along with housemates. Fight wound abscesses should be mentioned
here because they are closely related to deep skin infections. Abscesses
will be discussed in greater detail later on.
Deep bacterial skin infections usually appear as ulcerations/erosions of the
skin with swelling and crusts. Sometimes, draining tracts and swelling of
skin tissue known as cellulitis may also occur. If the skin in affected
areas is squeezed, pus material may ooze from weak areas in the skin
Diagnosis: To diagnose a bacterial skin infection, a cytology
(examination of a sample using a microscope) of a sample from the affected
tissue is usually performed. A trained professional will be able to see cells
associated with bacterial infections (neutrophils), as well as the actual
bacteria in many cases. Identifying the underlying irritants or causes
associated with the pyoderma is often more difficult. Specific skin tests might
be required to diagnose the underlying problem. These tests might include skin
scrapings for mange mites, cultures for fungal infections, blood analysis for
diabetes or cortisol hormone levels, skin biopsies, dietary food trials, allergy
testing, radiographs, or ultrasound. Additional information related to many of
the above tests can be found in Sections D and F.
Treatment: Treatment of bacterial skin infections is accomplished by both
removing the infection itself and removing the underlying cause. In cases of
superficial skin infections, the irritant of the skin (shampoo or cleaner, etc.)
may easily be avoided. In other cases, such as repeated self trauma due to itchy
skin, the offending cause may be extremely difficult to identify, let alone
avoid. Each situation must be dealt with on an individual basis, with the help
of a veterinarian.
Treatment of the infection itself is accomplished primarily with antibiotics.
A large variety of antibiotics exist that are effective against most pyodermas.
In cats, antibiotics of choice include penicillins (such as Clavamox or
amoxicillin), cephalosporins, enrofloxacin (Baytril), and clindamycin (Antirobe).
Fight abscesses are extremely common in cats that spend time outdoors or
fight with housemates. Fight wounds can occur anywhere on the cat’s body but
are most common on the face, limbs, rear end, and tail. Abscesses may become
large and extremely painful swellings, and they may slowly ooze a foul
discharge. Pasteurella species, streptococci, Corynebacterium
species, and Actinomyces species are common types of bacteria found in
cats’ mouths. Because they are common in cats’ mouths, they are also common
in fight abscesses. Diagnosis is generally made on physical examination by a
veterinarian. Owners with outdoor cats can also become extremely skilled at
identifying abscesses when they occur. Treatment of the abscess consists of
lancing and draining the abscess (often requiring anesthesia), flushing the
wound, and follow-up antibiotics. Clindamycin (Antirobe) and penicillins such as
Clavamox are antibiotics commonly used in treating feline abscesses.
Feline acne is a specific condition affecting the chin area of cats. The
cause of feline acne is not completely known. The infection can be superficial,
with small black scabs and crusts found periodically on the chin. It can also be
deep, with a painful swelling of the chin area and drainage of a mixture of
blood and pus. Diagnosis is easily made based on location and appearance of the
condition. Sometimes, an impression smear will be performed by a veterinarian to
determine the type of bacteria causing the infection. Treatment for mild,
superficial cases may consist of topical therapy only. Antibiotic/antifungal
creams such as Dermalone and benzoyl peroxide shampoos or gels may be applied
with some success. For severe, deep infections, oral antibiotics such as
Antirobe may be necessary.
Fungal Skin Infections:
Introduction: There are several types
of fungi that can infect the skin of cats. Most fungal skin infections can
appear identical to other types of infections (bacterial pyoderma and demodectic
mange); therefore, specific diagnostic testing should always be performed on a
suspected fungal skin infection to ensure an accurate diagnosis and treatment.
- Dermatophytosis (ringworm): Dermatophytes are a "keratinophilic"
(skin-loving) species of fungi that are responsible for the commonly known
syndrome "ringworm." Because the disease is not caused by a worm
at all, this term is rather deceptive. Ringworm is one of the most common
types of skin disease in cats.
Causative Agents: There are at least 20 different species of
dermatophytes that have been found to cause skin infections in cats;
however, the vast majority of feline cases are infected with one of these
Microsporum canis, Microsporum gypseum, and Trichophyton
mentagrophytes. Microsporum canis is the most common of these
Clinical Signs: Dermatophytosis in the cat appears very similar to other
infections of the skin. It is practically impossible to tell the difference
between dermatophytosis, demodectic mange, and some types of bacterial
pyoderma. Generally, these fungal infections appear as areas of hair loss,
with flaky, crusty, irritated skin. These areas usually cause some degree of
discomfort and itching to the cat.
Transmission: Cats can get ringworm in several ways. They can get the
fungi directly from humans, other animals (rodents, other cats, dogs), or
from the soil. They can also be exposed to fungi found on surfaces, such as
brushes, blankets, and bedding.
Diagnosis: A dermatophytosis infection is diagnosed by performing a
culture of the hair from an affected individual. This is accomplished by
taking hair samples from the outside edge of a few of the lesions. The hair
is then placed on fungal specific media and any dermatophytes are allowed to
grow. Most culture tests can be performed and interpreted by a veterinarian.
Results may take up to 10-14 days to provide an accurate answer. Other
techniques commonly used include a Wood’s lamp test and direct microscopic
examination of hair and scales of affected animals. Wood’s lamp testing
involves close examination of the skin of the animal with a special light
that causes the hair and skin to fluoresce a bright apple-green color if the
pet is infected with a dermatophyte. Wood’s lamp testing is only accurate
in about 50% of cases. Direct microscopic examination with the aid of
potassium hydroxide preparations is also done. This procedure, however, is
time consuming and a positive diagnosis may be made in only 50-60% of cases.
Treatment: There are a large variety of medications and treatment
options available for dermatophytosis therapy. Most often, a combination of
several types of therapy is utilized for maximum results.
Prevention and Public Health Concerns: Keep the cat’s skin healthy.
Because certain conditions encourage fungal growth, do not allow the cat’s
skin to remain damp and dirty. Dermatophytosis is "zoonotic,"
which means the disease is contagious to people. Care should be taken when a
pet is diagnosed with dermatophytosis. Follow the veterinarian’s
instructions completely when treating ringworm.
- Affected areas should be clipped; cases with widespread lesions should
receive whole-body clips. This may worsen the problem initially.
- Whole-body topical therapy should be used in all cases. Shampoos (chlorhexidine,
miconazole, or iodine based) and dips (lime sulfur, sodium hypochlorite, and
chlorhexidine based) are types of effective whole-body topical therapy that
can be used.
- Systemic therapy (treatments going to the entire body) should be used in
many cases. Systemic treatments include griseofulvicin, itraconazole, and
ketoconazole. Because griseofulvin is teratogenic (causes severe birth
defects), it should NEVER be used in pregnant animals and must be used with
great caution in breeding females. Systemic anti-fungals are usually very
expensive. Lufenuron, a drug generally used for treating flea and tick
infections in dogs and cats, has recently been advocated for use in ringworm
treatment in cats. The drug has not been officially approved for this use,
however, and should only be used for this purpose under the direction of a
If ringworm is identified on the cat, all bedding, combs, brushes, and cages
must be thoroughly cleaned and disinfected. A 1:10 dilution (1 part bleach
to 10 parts water) of household bleach can be used. The fungal spores remain
viable for up to 18 months in the environment. Frequent washing of hands,
bedding, and clothing that comes into contact with the affected animal is
very important. A thorough vacuuming of carpets, vents, and rugs is also
essential. Steam cleaning carpets may also help. A physician should be
contacted if people in the household become affected with skin
* For additional information on ringworm infections in humans and pets,
refer to F998.
Causative Agent: Sporothrix schenckii is a fungus that causes
skin infections in cats worldwide on a sporadic basis. In cats,
sporotrichosis is usually associated with a puncture wound or scratch caused
by the claws or teeth of another cat. This disease tends to occur more often
in outdoor male cats that like to roam and is frequently associated with
fight abscesses and wounds. Sporotrichosis occurs commonly on the head,
limbs, and base of the tail.
Clinical Signs: Affected animals have multiple nodules of infection in
the skin and tissues underlying the skin. These nodules may be ulcerated,
crusted, and have a draining discharge. If a limb is affected, the infection
may spread upward toward the body and may cause inflammation and infection
to occur in the lymphatic vessels and lymph nodes nearest the affected limb.
Secondary bacterial infections can occur. Sporotrichosis should always be
suspected in cats with fight abscesses or wounds that do not heal with
Diagnosis: Diagnosing this disease is usually much easier in cats than
in dogs. At body temperature, Sporothrix schenckii lives as a yeast
form that can be seen on cytology when present. These yeast forms exist in
high numbers in the infected nodules of affected cats and are usually
identified with relative ease. If cytology is unhelpful in diagnosing
sporotrichosis, other testing is available. Fungal culture is probably the
next most commonly successful diagnostic tool in the diagnosis of feline
sporotrichosis; however, results may take several days to a couple of weeks
before they are available. Submission of a sample of tissue for
histopathology is another method of diagnosis. When all other attempts at
diagnosis have failed, immuno-fluorescence staining of discharge or tissue
may be performed by the Centers for Disease Control and Prevention (CDC) in
Treatment: Treatment of Sporothrix schenckii infections may be
accomplished with the use of a supersaturated solution of potassium iodide (SSKI)
at about half the dosage used in dogs. This solution should be given orally
and then continued for at least one month after the nodules completely
subside (usually 4-8 weeks). Recurrence of infection is common when
treatment has not been administered for a long enough period of time. Side
effects of SSKI include vomiting, lethargy, weakness, twitching, and a drop
in body temperature. If side effects are severe, alternative therapy may be
offered. Such therapy includes ketoconazole or itraconazole, which are
general antifungal drugs. Cats have an increased sensitivity to these drugs,
however, and may not tolerate their use. Antibiotics for secondary bacterial
infections should always be a part of therapeutic plans for sporotrichosis.
Public Health Concerns: Transmission of sporotrichosis from cats to
humans is a risk that should not be overlooked. Human contact with the
discharge or wound infected with Sporothrix schenckii in a cat may
produce pustules, nodules, or painful inflamed growths in the skin of
humans. This risk does not appear to occur with canine sporotrichosis,
probably because there are so few fungal organisms found in the nodules and
discharge of dogs. Veterinarians and veterinary clinic staff, as well as
owners of infected cats, are at higher risk. Consultation with a physician
is recommended for human sporotrichosis.
Introduction: Blastomycosis is a fungal disease of animals and people
that is termed "systemic," meaning it affects many body systems.
Blastomycosis is extremely rare in cats.
Causative Agent: The organism that causes blastomycosis is called Blastomyces
dermatitidis and lives primarily in the Mississippi, Ohio, and Missouri
River Valleys; the mid-Atlantic states of Virginia, North and South
Carolina, and Tennessee; and the northern parts of Georgia and Alabama.
Clinical Signs: Difficulty breathing, skin infections with discharge
(especially of the paws), and weight loss are the most common clinical signs
Diagnosis: Blastomyces dermatitidis fungal infections can be
diagnosed by histopathology, cytology or both. The organism usually is seen
in more than 50% of histopathology or cytology specimens if the samples are
obtained and prepared properly. X-ray films of the lungs can be a helpful
tool in diagnosis. Serology is not considered a very reliable test for
diagnosis of feline blastomycosis.
Treatment: Treatment of blastomycosis is expensive, but the prognosis
for survival is generally good as long as the animal is not severely
debilitated. Itraconazole is currently considered the drug of choice for
treatment of cats with blastomycosis and is less likely to create problems
than its close relative, ketoconazole. Itraconazole can lead to inflammation
and irritation of the liver in cats and should be stopped temporarily if
jaundice (yellow tinge to skin and eyes) or loss of appetite is noted. No
vaccine is currently available for prevention of blastomycosis.
Parasitic Skin Infections:
Introduction: In speaking of the various parasites that infect the skin
of either people or animals, they are specifically referred to as "ectoparasites,"
meaning parasites that remain on the surface. In contrast, "endoparasites"
are those parasitic organisms whose life cycles favor the internal environment
of the body. The following are some of the most common ectoparasites found in
Ticks may attach themselves to any part of a cat and often cause a local
inflammatory reaction in the skin at the site of attachment. When attached to an
external location on the cat, the cause of the problem is usually readily
identified because the tick is quite large when engorged with blood. Sometimes,
the tick may attach itself in a more difficult area to access, such as inside
the ear canal. This can make diagnosing this problem more complicated.
Introduction: Fleas and flea allergies are among the most common
external parasite skin diseases seen in cats. Because fleas do better in
hotter, more humid environments, they are more of a concern in some areas than
others. The cat flea, Ctenocephalides felis, spends its entire adult
life on the cat. The entire flea population living on any single cat consists
of approximately 95% egg and larval stages, with adult fleas making up the
remaining 5%. Thus, it may be difficult to find the adult fleas on a patient,
even though the cat may suffer from a significant flea problem.
Clinical Signs: A range of problems may be seen in cats with flea
infestations. Minor infestations may go unnoticed in some cases or may cause
some itching (pruritus). In the very young or debilitated animal with more
severe infestations, blood loss may be significant enough to cause anemia.
Allergic reactions to the flea bite and secondary infections with tapeworms
are also common. Cats that develop fleabite hypersensitivity or miliary
dermatitis usually suffer severe itching (pruritus). They may develop hair
loss, thickened and/or discolored skin, and secondary bacterial infections.
Only one to two flea bites per week may be sufficient in supersensitized pets
to perpetuate the problem. Cats with underlying allergies (atopy, food
sensitivity) are prone to fleabite hypersensitivity.
Diagnosis: Diagnosis of a flea infestation is usually made by noting
the actual fleas or flea dirt (feces) on the skin of the animal. Pinpointing a
fleabite hypersensitivity problem, however, can be more challenging, since a
very minor infestation may be all that is present in such cases.
Crusting, open sores may be noted at the base of the tail and around the
neck of a cat with an allergic reaction to flea bites. Flea combs may be used
by veterinarians or pet owners to comb out evidence of fleas. Flea dirt is
often combed out and can be distinguished from other debris by placing the
suspected flea dirt on a moistened napkin. Because flea dirt is the excrement
from a parasite that consumes blood, it will leave light red stains on the
Other tests, including a blood sample (CBC) and skin biopsies, can be used
to help identify fleabite hypersensitivity. A specific type of white blood
cell called an eosinophil is commonly seen in both a CBC and in a skin biopsy.
Another aid for a veterinarian in the diagnosis of fleabite hypersensitivity
can be injecting the flea allergen directly into the skin and looking for an
Finally, specific flea treatment products may be administered, followed by
observation to see how the cat responds to the treatment. If the pet responds
favorably, a diagnosis of flea infestation can be made. Using treatment as a
"diagnostic approach" can be justified because most treatment
products are generally considered safe and affordable.
Treatment/Prevention: Treating flea infestations primarily focuses
on removal of the fleas from both the animal and the animal’s living
environment. First, eliminate fleas from the animal. There are many available
products. Some are obtainable through a pet store (over the counter), while
others are prescription drugs and are obtainable only through a veterinarian.
Over the counter products that may be helpful include flea combs, flea
collars, sprays, dips, powders, and shampoos. Insecticidal flea collars are
generally more effective than ultrasonic collar devices at reducing flea
infections. Sprays usually have rapid action but may be difficult to apply in
a thorough and consistent manner. Flea dips are generally rapid-acting and
long-lasting; dips may be given through a pet grooming facility or at home.
Flea powders are effective but messy and usually vary on how long they will
last. Flea shampoos are usually good for rapid killing of fleas but have no
residual (lasting) benefits. In general, using the over-the-counter products
alone is probably insufficient for adequately treating a cat with fleabite
hypersensitivity. Prescription products available through a veterinarian are
usually of great benefit to cats with fleabite hypersensitivity problems.
These products can be used for treatment and prevention. Many of these
products not only kill fleas but are effective against a variety of other
parasites including ticks, mites, intestinal parasites, and heartworm larvae.
Monthly pour-on (drip-on) formulations that are available include Frontline,
Advantage, and Revolution. Oral tablets are also available and include Program
Second, it is important to eliminate fleas from the pet’s living space.
This is accomplished with a thorough washing of carpets, rugs, and bedding,
followed by vacuuming furniture, baseboards, and even calling in a commercial
exterminator in more severe situations. Some advocate the use of foggers;
however, foggers may not be effective under furniture, and it is usually
necessary to utilize one fogger per room of the house. Some products, such as
Program, may be used on the affected animal(s) in order to prevent flea
development and keep the eggs from hatching in the environment. An effective
treatment plan must involve three things: treating the pet’s environment,
treating the affected pet, and treating all other pets that have contact with
the affected pet. Failure to thoroughly address all three of these areas can
result in continued and repeated flea infestations. (See F998
information on flea problems in humans and pets.)
Introduction: Ticks are a common bloodsucking ectoparasite that can
cause skin disease in cats. There are many different species of ticks that can
be found throughout the world. The most important health problem associated
with ticks is not the skin disease they cause as much as the diseases they can
transmit. Ticks are responsible for transmitting a large number of microbial
diseases to cats and other species, including man. Some of the diseases ticks
are responsible for transmitting may be life-threatening to cats and people.
Babesiosis (piroplasmosis), Cytauxzoonosis, feline ehrlichiosis, tularemia, Q
fever, and possibly Lyme disease are all infectious diseases that are
transmitted by ticks to cats.
Once the problem is identified as an attached tick, removal must be performed.
Because mouthparts have usually not yet become embedded in the skin, removal is
usually quite easy if done within the first hours after attachment. Cautiously
removing each individual tick with thumb forceps is acceptable for some species
of tick; however, other species secrete a type of cement that may make complete
removal much more difficult. Leaving mouthparts embedded in the skin may cause
irritation and secondary bacterial infections. If the tick cannot be safely
removed, there are many different products that are very safe and effective at
treating tick infestations. These products are listed under prevention.
Prevention: Treatment for the various microbial diseases ticks can
transmit is often complicated and costly. Sometimes, the pet may die in spite of
aggressive treatment. Because of this, prevention of tick infestations is of
great importance. A variety of quality products exist that may be administered
before a pet is taken into an area known to harbor ticks. Over the counter
products that may be helpful include collars, sprays, dips, powders, and
shampoos. Insecticidal flea/tick collars are generally more effective than
ultrasonic collar devices. Sprays usually have rapid action, but may be
difficult to apply in a thorough and consistent manner. Dips are generally
rapid-acting, long-lasting, and may be given through a pet grooming facility or
at home. Tick powders are effective but messy and usually vary on how long they
will last. Shampoos are usually good for rapid killing of ticks, but some have
no residual (lasting) benefits. Prescription products are generally extremely
effective, long-lasting, and safe. Pour-on (drip-on) formulations that are
available include Frontline and Revolution. (Specific information on both of
these products can be found in Section C of this manual.)
Introduction and Causative Agents: Two types of mite infections occur
frequently in cats. Notoedres cati, the mite responsible for notoedric
mange, and Cheyletiella blakei, the mite responsible for cheyletiellosis,
are both common in cats. Other mites such as Demodex species and chigger
mites occasionally can also cause disease. The ear mite, Otodectes cynotis,
is also a very important mite infection in cats, generally limited to the ear
Note: The use of ivermectin in some of the following treatments is
considered "extra-label;" therefore, a veterinarian must be consulted
before administering it to a cat.
- Notoedric mange: Notoedres cati is a sarcoptic mite that
causes a skin disease in cats similar to sarcoptic mange in dogs. This mite is
very contagious and can also infect dogs, rabbits, and humans. Notoedric mange
usually starts with itchiness and scratching at the head, ears, and neck, with
crust formation. Later, the disease may spread to other areas of the body,
especially the legs and the groin area. Secondary damage to the skin from the
cat’s own scratching often leads to secondary bacterial or fungal
infections. Lymph nodes may be swollen and tender.
Diagnosis of notoedric mange is usually made with skin scrapings that are
then examined using a microscope. If the diagnosis cannot be made with a skin
scraping, skin biopsy and histopathology can also be helpful.
Treatment of notoedric mange in cats begins with clipping and cleaning of the
affected areas. Lime sulfur dips can be used to cure this infection. They are
given once weekly until the skin is back to normal. Another treatment option
involves giving two or three ivermectin injections. Revolution can be used in an
extra label manner to treat cats with notoedric mange. Treatment of all cats on
the same premises is critical in preventing this disease from recurring.
- Cheyletiellosis: Cheyletiella blakei is a rather large mite
that tends to cause flaking and dandruff on the back of cats. As the mites move,
the large flakes of dandruff will move around as well. Because this movement is
visible to the naked eye, the term "walking dandruff" is used.
Cheyletiellosis can also affect dogs, rabbits, and humans. Itching ranges from
completely absent to severe. Scaling (dandruff) is very common with
cheyletiellosis, and its presence can be very helpful in making a correct
Diagnosis of cheyletiellosis is made by
direct observation of the mites and/or their eggs. Mites and eggs may be
collected from an infected individual by skin scrapings, tape preparations,
combings, vacuum techniques, or analysis of the feces.
Treatment of cheyletiellosis may include
weekly lime sulfur dips for 3-6 weeks, oral ivermectin treatments weekly for 4-6
weeks, or subcutaneously injected ivermectin every 2 weeks for 3 treatments.
Many medications used to control fleas may also be successful at treating Cheyletiella
blakei infections. Because this mite can live off of the host for a longer
period than most mites, maintaining a clean environment is very important in
successful management of this type of mange. Frequent vacuuming of carpets and
rugs, washing of the bedding, and treatment of all dogs and cats in contact with
an infected pet are all important in helping to prevent re-infection of treated
animals. For more information on mites in humans and pets, see F998.
- Demodectic mange (demodecosis):
Feline demodecosis is uncommon. Demodex cati, Demodex gatoi,
and an unnamed species of Demodex are found in cats with this mange mite
infection. Cats suffering from demodecosis usually have patches of hairless,
reddened, itchy skin with crusts. Localized Demodex infections are most
common, but generalized infections can also occur. Purebred Siamese and Burmese
cats seem to have more problems with generalized demodecosis than do other cat
breeds. Sometimes, cats may suffer from Demodex infections of the ear
canals. Demodex gatoi is contagious to other cats; therefore, all
household cats should be treated when any case of feline demodecosis is
Diagnosing demodectic mange is accomplished by first taking scrapings of the
skin. When taking a skin scraping looking for demodectic mange, it is important
to get a small amount of blood with the sample. The reason for this is that the
mites live relatively deep in the hair follicles (although not as deep as the
dog variety of Demodex mite). If small capillaries of blood are
reached/ruptured with the scraping, the scraping is deep enough to include these
mites in the sample. The mites themselves are then identified microscopically.
Because Demodex mites infecting cats do not appear to burrow as deeply
into the skin and hair follicle, successful treatment in cats is usually easier
than it is in dogs. Topical products like benzoyl benzoate ointment (Goodwinol
ointment), lime sulfur dips, and carbaryl shampoos can be used with success.
Weekly amitraz dips can also be helpful. Ivermectin injections have also been
used in treatment, although not as frequently as with demodecosis in dogs.
Antibiotics may be used if secondary bacterial infection occurs.
- Otodectes cynotis is a common mite that is found mainly in
the ear canals and adjacent skin of cats, dogs, and ferrets. Dark waxy debris is
common with infestations of Otodectes cynotis, and intense itching of the
ears usually accompanies such infections. Some cats that suffer from ear mites
may shake their heads so violently because of irritation that they develop an
aural hematoma (a very painful swelling of the ear pinna or thin part of the
ear). Secondary ear infections with bacteria and/or yeast are common with ear
Diagnosis of ear mite infections is made by observing the mites using a
microscope. A cotton-tipped swab is placed into the ear canal and a sample of
the dark waxy debris is collected and examined under magnification.
Many treatments for ear mites exist, some of which can be found over the
counter in pet shops and stores. Because ear mites are very contagious between
animals, it is important to treat all in-contact dogs and cats as well as the
affected pet. Regardless of the treatment selected, a thorough cleaning of the
ears is the first step to clearing up an ear mite infection. Rotenone-based ear
drops or washes can be used with some success. Ivermectin administered either
subcutaneously or directly into the ears may also be used, but results are
unpredictable. Finally, selamectin (Revolution) has recently been approved for
treatment of ear mites in cats and kittens, and it appears to be a very safe,
effective, inexpensive, and simple means of treating Otodectes cynotis
Introduction and Causative Agents: Most lice are extremely
species-specific, which means that they are adapted to one type of host animal
(or human) and are unlikely to be contagious to other species of animals. They
can be, however, very contagious to other individuals within the same species. Felicola
subrostratuas is a chewing louse adapted to cats.
Clinical Signs: Lice are
parasites of the skin that cause mostly superficial skin inflammation and
itching. Some cats infected with Felicola subrostratuas can suffer severe
itching and hair loss on the back.
Diagnosing an infestation with lice is made by identifying the parasite using a
microscope. Careful observation of the anatomy of the louse will aid a
professional in identifying the specific species causing the infection. This is
important in order to determine the most likely source of the louse infection
and to aid in preventing re-infections.
Treatment: Treatment of lice infections in cats is accomplished with
the use of carbaryl shampoos or dioxathion shampoos, sprays, or dips. Usually,
treatment is administered and repeated weekly until the lice infestation has
resolved. Two or three treatments are usually sufficient. Fipronil (Frontline)
sprays can also be effective in cats.
Allergic Skin Disease
Introduction: Allergic skin disease
can occur in cats but does so less frequently than in dogs. Allergic skin
disease is broken down into three major categories based on how the offending
substances that cause the allergic reaction enter the body. Recently, how these
category headings are broken down has come into some controversy. This is
because a given substance that causes an allergic reaction may actually enter
the body through many different avenues. It is actually quite important to
understand this when treating an allergic skin condition. In general, allergies
result from an exaggerated response to a foreign substance (allergen) that the
immune system perceives as a threat to the body.
Treating atopy is another area of challenge. Treatment is broken into 2 major
categories: immunotherapy and non-immunotherapy.
- Atopic or Allergic Inhalant Dermatitis:
Introduction: The term allergic inhalant dermatitis implies that the
cat has inhaled the substance(s) that causes a reaction in the skin. Atopic
dermatitis is a less restrictive term, implying that the allergic reaction is
a response to ordinary environmental substances. Many studies indicate that
atopic dermatitis may result from not only inhalation of these ordinary
substances but also through ingesting these substances or when these
substances directly contact the skin. Because of this new understanding, the
term allergic inhalant dermatitis is falling out of favor.
Atopy is a general term commonly used to describe these types of allergic
reactions. Atopy is often considered an inherited problem passed on through
genetics. All cat breeds and both male and female cats appear to be equally
affected. Cats younger than 3 years of age seem more likely to become
Causative Agents: Cats can be allergic to a variety of things including
flea saliva, house dust, house mites, air-borne molds, human dander, and
regional pollens to name a few. All of these are considered allergens or
substances that produce an allergic reaction. When one of these substances
contacts the animal, the immune system produces several types of antibodies
known as immunoglobulins. Most of these have the absolutely crucial function
of fighting infection. One specific type of antibody, known as Immunoglobulin
E (IgE), plays a significant role in allergic reactions. Basically, the immune
system of cats with atopy overreacts and a hypersensitivity reaction results.
This hypersensitivity reaction produces excess IgE and causes the release of
histamine and other substances. IgE is generally found in high levels in cats
that suffer from atopy.
Clinical Signs: The signs of atopy include mild to severe itchiness
(pruritus) and skin redness. Hair loss (alopecia) and thickening of the skin
are also possible. Secondary bacterial or yeast infections are common and may
result in drainage of pus, crusting, and further itching. Many areas of a cat’s
body may be affected depending on the pattern of atopy present. Four reaction
patterns occur in cats in response to atopy. The first reaction pattern is
called "fur mowing." This is where the cat chews its own hair out,
leaving bald, reddened patches all over its body. Secondly, eosinophilic
granuloma plaques may occur, in which the skin becomes reddened and thickened
and hair falls out. The third type of reaction pattern is called "miliary
dermatitis." It is a common secondary reaction to skin infections in the
cat and produces crusting and intense itching all over the body.
Itching/scratching of the face, ears, and neck in the absence (initially) of
any visible skin problem is the fourth reaction pattern. Atopy is usually not
seasonal in cats, indicating that cats tend to react more to house mites and
other nonseasonal allergens.
Diagnosis: The diagnosis of atopy is somewhat of a challenge. In
many situations, no formal testing is done, and the diagnosis is made based on
history, clinical signs, and response to treatment. Testing is available,
however, and can be extremely beneficial for cats suffering from atopy.
Because the testing is usually expensive, and the results can be difficult to
interpret, it should be reserved for cats that are experiencing the most
The intradermal skin test is generally accepted as the best test available
for the diagnosis of atopy. To perform this test, an experienced veterinarian
(usually a veterinary dermatologist) injects small blebs of reagents/allergens
to which cats are known to react directly into the skin. Allergic cats will
react by forming a lump or "wheal" in the area associated with the
specific injection(s). Sedation is generally very helpful when performing the
test and helps to decrease interference with natural steroid release from an
excited or anxious animal. The pet undergoing an intradermal skin test should
not be treated with any corticosteroids (i.e. prednisone) for at least 6 weeks
prior to testing. The steroid can prevent the skin from reacting to the test
injections. This test is very dependent upon the experience of the
professional performing the procedure and the interpretation of the results.
The second type of testing commonly used
in the diagnosis of atopy is serologic allergy testing. Currently, three major
types of serology tests are available that can be used for diagnosing atopy:
ELISA (enzyme-linked immunosorbent assay), RAST (radioallergosorbent test), and
liquid-phase immunoenzymatic assay (VARL). Blood from a suspect atopic cat is
sent to a laboratory for measurement of IgE levels against specific allergens. A
detailed history of the condition and the region of the country where the cat
resides are also included. Testing is performed on the blood using a variety of
allergens (regional pollens, house dust, house mites, air-borne molds, human
dander, and often food proteins) to which the cat may be reacting. These tests
measure IgE levels in the animal’s blood and report any allergens where there
is a high IgE response.
- Immunotherapy, also known as hyposensitization, consists of
desensitizing the cat’s immune system to the allergen or allergens that
cause the allergic reaction. In order to offer this type of therapy, either
intradermal skin testing or serologic allergy testing must be performed to
specify the exact offending allergens to be desensitized against. The way
hyposensitization works is fairly complex. Small measured amounts of the
specific allergen(s) to be desensitized against are injected regularly under
the skin. These injections may be administered at home or in a veterinary
hospital. A specific schedule with the frequency and amount of each injection
is outlined and strictly followed. Studies show that between 50% and 80% of
treated animals have a good to excellent response. While considered as
probably the best treatment option by many for controlling atopy in cats,
hyposensitization treatment is not often used. Further research needs to be
done in the area of immunotherapy to help better understand all the factors
that affect the success of treatment. This will help the veterinarian select
the best candidates for a successful response to this type of therapy.
- Non-immunotherapy is a collection of medications used in the
treatment of atopy and other types of allergies. Each category will be briefly
discussed here under the heading of atopy, but it should be remembered that
all types of allergies may respond to one or a combination of the medication
- Corticosteroids: Corticosteroids are a class of powerful
antiinflammatory drugs that are commonly used in the control of atopy.
Corticosteroids given systemically (orally or by injection) are necessary to
help control atopy in a large number of cases. Cats tend to require higher
dosages of corticosteroids than dogs do for an adequate response.
Prednisone, prednisolone, methylprednisolone, triamcinolone, and
sometimes dexamethasone can be used in cats. Corticosteroids are generally
inexpensive but can have undesirable side effects. These side effects
include the excessive need to drink water and urinate, appetite changes,
behavior or personality changes, and liver irritation. Because of these side
effects, the main goal with corticosteroid therapy is to control the
condition adequately on the lowest possible drug dose. Steroid injections
given weekly to every few months may be sufficient to manage a cat with
atopy. Oral steroids may also be used in cooperative cats on a daily to
twice daily basis. Many of the following medications may be used with the
attempt to reduce the need for corticosteroids.
- Antihistamines: Antihistamines are a class of anti-itch therapy drugs
used commonly in people with allergies. There are several types of
antihistamines available. Antihistamines may be synergistic (more effective
if given together than separately) with essential fatty acids. Some
available antihistamines that may be utilized in the treatment of allergic
skin problems include diphenhydramine (Benadryl), hydroxyzine,
chlorpheniramine (Chlor-Trimetron), cyproheptadine, and clemastine (Contac).
It has been suggested that a first attempt at treating a cat with atopy (if
non-immunotherapy is to be pursued) begins with essential fatty acid
treatment and then multiple two week trials of several different
antihistamines. If a combination is found to be beneficial to the cat, this
therapy may be used either exclusively or in combination with other
medication based on need. If no antihistamine is found to be effective,
corticosteroids are then used. Perhaps the greatest disadvantage of
antihistamine use in cats is the fact that it is an oral medication that
requires lifetime administration if used to treat atopy. This, probably more
than any other reason, discourages the use of antihistamines in cats.
- Essential fatty acids: Essential fatty acids (EFA) are composed of
Omega 3 and 6 fatty acids, with the most emphasis on the Omega 3 fatty acids
to best control itching. EFAs should be given for at least 3 months to
observe maximal benefit. EFAs are considered to be very safe, with adverse
side effects occurring only very rarely. EFAs are generally given daily as a
capsule or liquid.
- Topical therapy: A large number of topical medications exists that can
be helpful in cases of atopy. Most of these products, however, must be used
along with other therapy and not as the sole treatment for allergies. By far
the most cost-effective is cool-water bathing, which may give relief for up
to 1-2 days. Cool-water baths may be very difficult and traumatic for cats,
however. Other types of topical therapy include shampoos/conditioners,
creams, ointments, and sprays. Shampoos that reduce pruritus (itching) may
contain oatmeal (see page G207), local anesthetics such as pramoxine,
antihistamines such as diphenhydramine, and corticosteroids such as
hydrocortisone. Cooling agents such as camphor and menthol may also be
helpful in replacing the itch with a cool sensation. Dry skin increases the
sensation of itching and may be alleviated with skin moisturizing ointments,
shampoos, or emollients such as fatty acids, glycerin, and oatmeal. Sprays
may contain antihistamines, corticosteroids, or local anesthetics.
- Dietary therapy: Dietary therapy is generally beneficial to those
animals suffering specifically from food related allergies (discussed
below). For animals that suffer from food allergies, dietary therapy is the
primary treatment. A variety of "low allergy" or hypoallergenic
diets exist. Many of these diets may be purchased as over-the-counter diets,
while others are sold only as prescriptions through veterinary hospitals and
clinics. Many of the diets available only by prescription through
veterinarians are used in the most severe cases. Cases that use the
prescription diets tend to have a greater success rate than those that use
only the over-the-counter-diets. There are so many types of diets that may
be used in food allergies that no attempt will be made here to list them.
See the section on food allergies for more information on the properties of
these hypoallergenic diets.
Introduction/Causative Agents: Allergic skin disease resulting from an
adverse reaction to food is responsible for up to 20% of all skin related
allergies in cats. Food allergies along with food intolerances make up a broader
category known as food sensitivities.
Food allergies are due to a reaction by the body’s immune system to certain
substances (allergens) in food. Food intolerances do not involve the immune
system and are usually due to certain types of food such as dairy products. It
generally takes some time for a cat to develop an allergy to food, and some cats
may eat the same diet for years before they begin to react to an ingredient.
Allergens that are most commonly associated with food allergies in cats include
beef, dairy products, and fish.
Clinical Signs: The signs of
food allergy in cats are similar to atopy. They include moderate to severe
itchiness, redness, and skin erosions often restricted to the head, face, and
neck. Sometimes, "fur mowing" (self-induced baldness without obvious
initial skin problems) and eosinophilic plaques will also occur. Vomiting,
diarrhea, and mouth inflammation may accompany skin problems in cats with food
allergies. Like atopy, secondary bacterial or yeast infections are common. Food
allergies are not seasonal.
Diagnosis: The diagnosis of
food allergy is accomplished with a dietary trial. During the trial, a diet with
a limited number of possible food allergens is fed for 6-8 weeks. Throughout the
trial, additional food and food products (table scraps, snacks, or palatable
medications) must be eliminated. The diet itself can be either home-made or
commercial, but it must contain only carbohydrates as a base and one protein
type to which the cat has never or only rarely been exposed. Such protein
sources can include lamb, rabbit, or venison. Rice or potato may be added but
are usually avoided by the cat. Homemade diets are usually the best. Commercial
hypoallergenic diets can be used for the dietary trial but are less successful
since there is no commercial diet that works for all cats with food allergies.
If after 6-8 weeks, the cat has shown some improvement with a strictly followed
dietary trial, the diet is then continued until maximal improvement is noted. To
confirm the diagnosis, the cat is then given its previous diet. Clinical signs
should recur within 7-10 days. If there is no response to a diet trial after 6-8
weeks, a different type of hypoallergenic diet may be fed. If the cat continues
not to respond to the dietary trials, food allergies are not likely the cause,
and further testing is necessary to find the correct diagnosis.
Treatment: Proper treatment for
food allergic animals is life-long maintenance with a diet that the animal can
tolerate without experiencing skin reactions. For life-long maintenance, it is
best to feed the cat a high quality, hypoallergenic commercial brand food or a
balanced homemade diet. Many cats with food allergies will do very well on a
commercial hypoallergenic brand of food, although some experimentation may be
required to find a brand and ingredient combination that will be well tolerated.
Cats fed a homemade diet often require vitamin and mineral supplementation to
avoid nutritional deficiencies. Corticosteroids may be used if a restricted diet
is not successful or not possible (i.e. cats that hunt for their own diets).
Allergic Contact Dermatitis:
Introduction: Allergic reactions to substances that directly contact
the skin can affect the general condition of the animal or may simply cause a
local reaction in the area of contact. Reactions that remain localized to the
area of contact are known as contact allergic reactions or allergic contact
dermatitis. It may become confusing when a cat experiences allergic contact
dermatitis due to a substance, such as a shampoo or body rinse, that has
contacted the entire body. These cases where the problem extends over the entire
body may appear at first to be a case of atopy (see F770). Contact
dermatitis is considered rare in cats, with the possible exception of miliary
dermatitis. Miliary dermatitis, discussed previously as one of four reaction
patterns in feline atopy, may be thought of as a type of contact dermatitis in
which the skin reacts to the presence of an infection such as fleas or fungus (dermatophytes).
Causative Agents/Clinical Signs: Many
cases of contact dermatitis are caused by infections, medications, shampoos,
bedding, chemicals, cleaning agents, or other similar products. When contact is
made with these substances, the body’s immune system reacts by changing the
skin in the area where the contact is made. The ears, abdomen, back, thighs,
feet, tail, and chin may become involved. When an allergic reaction occurs in
these areas, the skin is red, inflamed, can be itchy (pruritic), and have bumps
or blisters (vesicles).
To diagnose allergic contact dermatitis, a thorough history is essential.
Information on the types of medications or shampoos used recently, any ongoing
infections the cat may be experiencing, bedding type, and any contact with
chemicals, cleaning agents, or other similar products is extremely helpful.
The treatment of allergic contact dermatitis focuses primarily on avoiding the
substance/medication or treating the infection that led to the reaction.
Corticosteroids may be used either systemically or topically to relieve
immediate itching and discomfort.
Autoimmune Skin Diseases
Introduction: Autoimmune skin diseases
(also known as immune-mediated disorders) are best described as conditions where
the body’s immune system is directly responsible for damage done to the skin.
Allergic skin disease is also traced to the immune system but is a result of a
more indirect reaction. Allergies result from an exaggerated response to a
foreign substance (allergen) that the immune system perceives as a threat to the
body. Autoimmune skin disease is a result of direct attack by the immune system
on the skin itself. When compared to skin disease as a whole, autoimmune
disorders are much less common than either infectious or allergic skin disease.
Autoimmune diseases are broken down into primary and secondary disorders.
Primary disorders are those that develop spontaneously, independent of any
external triggers. Secondary disorders are a result of a triggered response,
traceable to a variety of stimulating factors such as certain drugs, bacteria,
or viruses. The following will address three major types of autoimmune diseases:
Diagnosing DLE is based on history, clinical signs, physical examination, and
skin biopsy. A biopsy is necessary for a positive diagnosis and is generally
very well tolerated with a quick recovery.
- Pemphigus Complex: There are 3 main varieties of pemphigus
reported in cats: pemphigus foliaceous, pemphigus erythematosus, and pemphigus
Clinical Signs: The clinical signs for pemphigus complex diseases vary
depending on the type of pemphigus the animal has developed. These differences
have been described to some extent in the preceding information. In general,
the affected areas are covered with pustules, crusts, and/or ulcerations of
the skin. Drainage of a clear to yellow/brown discharge and cracks in the
affected skin, deep enough to allow bleeding, are common. Secondary infections
are frequently seen. Itching (pruritus) is also extremely common with all
forms of pemphigus. Sometimes, a coming and going progression of the disease
is noted. This can be accompanied by the sudden (hours to days) appearance of
new pustules in previously unaffected areas. This is followed by days to weeks
of crust formation over the previously affected areas.
- Pemphigus foliaceous is the most common form of the pemphigus
complex seen in cats. Pemphigus foliaceous primarily affects the face, feet,
ears, and nipples. Normal dark coloration of the nose may lose pigment and
change to a lighter color. This may result in "photodermatitis."
Photodermatitis is a term which implies a skin disorder that worsens with
exposure to sunlight.
- Pemphigus erythematosus is usually thought of as a form of
pemphigus foliaceous that is confined to the face and ears. Like pemphigus
foliaceous, loss of pigment in the nose and resulting photodermatitis may
- Pemphigus vulgaris is extremely uncommon. This is fortunate,
because it carries the poorest prognosis of the pemphigus complex disorders.
Many cases of pemphigus vulgaris are unmanageable or manageable for only a
short period of time. Frequently, euthanasia is the ultimate outcome. This
condition does not seem to be associated with any age, sex, or breed types.
The feet, face, mouth, armpit (axilla), groin (inguinal area), anus, vulva,
and prepuce may be affected. Many cases develop ulcers and inflammation in
the mouth, leading to difficulty eating and bad breath.
Diagnosis: Diagnosing pemphigus complex autoimmune diseases is
generally made by a skin biopsy and histopathology. History and physical
examination provide extremely important information that is necessary in
helping to establish a diagnosis. Feline leukemia (FeLV) and feline
immunodeficiency virus (FIV) testing should also be performed in any cat with
a suspect autoimmune skin disease. Direct smears with special stains of the
crusts and skin discharge may also provide useful information in arriving at a
diagnosis of pemphigus foliaceous. Finally, there are special tests that may
be run by a laboratory specializing in skin samples. These tests include
immunofluorescence and immunohistochemical testing, and can confirm a
suspected diagnosis of pemphigus complex disorder.
Treatment/Management: Treatment and management of the pemphigus complex
diseases are based on suppressing the immune system’s attack on the skin. In
doing so, it is important to establish a specific diagnosis of the type of
pemphigus. This is critical because the different pemphigus disorders have
different management techniques and vary on their response to treatment.
Pemphigus vulgaris, for example, is difficult to manage and is often fatal,
while pemphigus foliaceous is less severe but may be fatal without treatment.
Pemphigus erythematosus is much easier to manage and carries a good prognosis
Therapy is usually initiated with large doses of corticosteroids (prednisolone)
to induce remission of disease. After a favorable response, the dosage may be
decreased. Many cases may be managed on corticosteroids alone.
In cases where management with corticosteroids alone is incomplete or
inappropriate, other drugs that suppress the immune system may be used.
Aurothioglucose or chlorambucil may be added to the corticosteroid treatment.
Because it can quickly lead to a fatal blood condition, azathioprine, commonly
used in dogs with resistant pemphigus disease, should be used with extreme
caution or not at all in cats. Doses of immunosuppressive drugs needed to
manage pemphigus complex diseases are usually high, and it is important to
consider the problems associated with these treatments. Most animals will
experience side effects, including a weakened immune system, and may be more
susceptible to infections. Boarding, grooming, cat shows, or any other
circumstance where the treated cat will be exposed to other cats may need to
be off-limits to help prevent spreading of infections. Even exposure to a
common upper respiratory virus in an animal with a drug-induced weakened
immune system may prove to be very serious. It has been shown that exposure to
sunlight tends to worsen many cases of pemphigus complex, and the use of
sunscreen lotion on affected areas or avoiding the sunlight altogether may
help with therapy and management of these disorders.
- Lupus Diseases:
Introduction: Lupus erythematosus is a group of autoimmune diseases
where lymphocytes attack the body’s own tissues. Lymphocytes are a type of
white blood cell that normally help fight infection. Lymphocytes come in a
variety of types, each with a specific function in the immune system. In lupus
diseases, different lines of these lymphocytes attack the body’s own tissues
and produce disease. Lupus diseases are relatively uncommon, with two major
types occurring in the cat.
- Systemic Lupus Erythematosus (SLE): This is a rare illness
where the lymphocytes attack a wide variety of tissues. Because of the
variety of tissues that may be attacked, the clinical signs associated with
this illness are also extremely varied and seem to mimic a number of other
diseases. SLE has been called "The Great Imitator" due to this
variety of signs/symptoms and the tendency to mimic other disorders. Among
the tissues that may be attacked is the skin. About 20% of cats with SLE
have skin involvement. SLE may produce hair loss, scale
("dandruff"), skin redness, itching, ulcerations, vesicle
(blister) formation, overgrowth of the footpads, and persistent secondary
bacterial infections of the skin. Any combination of these may be noted in
small areas of the skin or may affect the entire body. The face, ears, and
paws seem most likely to be affected in cats.
Diagnosis: Diagnosing SLE is extremely difficult. There is no
single test that can specifically diagnose SLE. Tests that may be helpful in
establishing a diagnosis include bloodwork (CBC, serum chemistry profile),
FeLV and FIV screening, and urine analysis. A test called ANA (anti-nuclear
antibody) testing can also be used in the diagnosis of SLE; however, this
test seems to be somewhat unreliable in cats. This test looks for immune
system activity against certain portions of the body’s own cells. Joint
taps (if arthritis is present) and skin biopsies (if skin disease is
present) are also beneficial.
Treatment/Prognosis: Treating SLE is based on the body systems
affected. Generally, drugs that suppress the immune system are the key in
managing this disease. Corticosteroids, gold salts, and chlorambucil are the
main drugs that are used in treating feline SLE. Antibiotics for secondary
infections are commonly used. The prognosis is guarded because many cases
develop organ failure (i.e. kidney failure, liver failure) or blood
- Discoid Lupus Erythematosus (DLE): This is a more benign cousin
of systemic lupus erythematosus. In DLE, lymphocytes attack the nose and
occasionally regions around the eyes, ears, lips, and chin.
Clinical Signs: A history of crusting in the described areas (nose,
eyes, ears, lips, and chin) is the most common clinical sign. Some cats may
experience pruritus (itching), with secondary self-inflicted damage to the
differs according to the severity of an individual case. Minor cases may
benefit greatly by reduced exposure to sunlight and/or the use of topical
treatments such as corticosteroids and dimethyl sulfoxide (DMSO). DMSO fights
inflammation and is available in a gel form. Moderate to severe cases may
require more aggressive therapy. Corticosteroids are usually considered the
therapy of choice in treating feline DLE.
Introduction/Causative Agents: Erythema multiforme is an uncommon
autoimmune illness of the skin that affects cats. It is thought that this
condition represents a sudden attack by the immune system on skin tissue that is
brought on by certain triggers. The most common triggers thought to lead to
erythema multiforme in the cat are drug reactions. A variety of drugs have been
associated with this problem, including penicillin and gold salts.
Erythema multiforme begins with symmetrical red patterns that may progress to
blister-like areas and eventually to tissue death and sloughing.
Diagnosing this disease is based on history, physical examination, clinical
signs, and skin biopsy.
Treatment: Treatment of
erythema multiforme focuses on correcting any underlying cause. If the
underlying cause is removed, the condition itself usually resolves within a few
weeks without any specific treatment. Severe cases have been treated
successfully with drugs that suppress the immune system (corticosteroids).
Neoplastic (Tumors and Cancer) Skin Problems
Introduction: Skin tumors and cancers
are seen quite often in cats, and the list of tumor types and cancers is long.
Some grow slowly as single or solitary lumps and do not tend to spread beyond
the immediate tumor area. Others may grow quickly, involve large or multiple
areas of the skin, and may spread to internal organs causing a life-threatening
situation. Tumors can be benign (less invasive, less destructive) or malignant
(invasive, destructive, and may spread).
Identification of the tumor type or class is extremely important when facing
a possible skin cancer situation. There is no way to predict what any tumor will
do or how serious a skin lump may be without a specific diagnosis.
Diagnosis: The diagnosis of skin tumors or lumps is based primarily on
biopsy or removal of the tumor and subsequent histopathology. Some are possible
to diagnose with a fine needle aspirate and cytology. This does not require
anesthesia, but a specific diagnosis is usually not possible with this
Treatment: Treatment of skin tumors and malignant cancer types varies
with the specific tumor. Removal of the tumor is usually at the top of the list
of treatment recommendations. In many cases, removal of the tumor cures the
disease. Tumor removal techniques vary a great deal and range from a simple snip
excision to amputation of an entire limb. Other treatment recommendations may
include radiation therapy, chemotherapy, hyperthermia (heat therapy), and
cryotherapy (freeze-burning). Nutritional cancer therapy is a field that has
received much attention in the last decade. Prescription diets that appear to
have benefit in slowing the growth of many types of cancer are commercially
available through veterinary hospitals. See the information on page E495 for
additional details on the diagnosis and treatment of tumors in general.
The following list of tumors and skin cancer types is not meant to cover all
the possible skin tumors but will include many of those most common in the
feline patient. The purpose is to give cat owners a brief description of
the tumor or skin cancer type after a diagnosis has been made. This list
is not intended to provide the diagnosis of a lump or tumor. These tumors
and cancers are listed in order of how frequently they are diagnosed in cats
living in the United States.
Mast cell tumors of the skin may appear as distinct lumps or as multiple varying
sized lumps in the skin. They occur most commonly on the head and neck of cats.
They may be slow or fast-growing. Sometimes, cats may develop so many tumors
that it becomes nearly impossible to treat them surgically because of sheer
numbers. Mast cell tumors have the potential to spread internally and cause
life-threatening disease, although the vast majority of feline MCTs are benign.
A syndrome seen in young Siamese cats called histiocytic mast cell tumor
syndrome will often regress (return to previous state) on its own.
- Basal Cell Carcinomas:
Introduction: Basal cell tumors, both benign and malignant, are the
most common type of skin tumor seen in cats. Basal cell carcinomas are a large
class of tumors arising from skin and a few other tissues. These tumors are
associated with exposure to ultraviolet light in people, but this correlation
has not been proven in cats.
Clinical Signs: These tumors are usually slow-growing, firm, rounded,
and may ulcerate on the surface. Basal cell carcinomas are also frequently
pigmented and may have the dark appearance of a melanoma. While the term
"carcinoma" implies a malignant growth, basal cell carcinomas are
considered to have a low grade of malignancy and rarely spread beyond the
Diagnosis/Treatment: Histopathology will identify this type of tumor.
Treatment may be achieved by surgical removal of the tumor or cryotherapy.
- Squamous Cell Carcinoma:
Introduction/Causative Agents: Squamous cell carcinoma (SCC) is
probably the condition most frequently associated with the term "skin
cancer." SCC arises from the most superficial layer of skin and is
associated with exposure to excessive sunlight, virus infections of the skin,
radiation, burn and frostbite scars, and chronic skin irritation. SCC is not
found more commonly in certain breeds; however, white cats develop this type
of cancer much more frequently than do cats of other colorations. The average
age of diagnosis in cats is 9 years.
Clinical Signs: The most common
areas for development of SCC in cats are the nose, the tips of the ears, the
eyelids, and the lips. SCC also occurs frequently inside the mouth of cats. SCC
may either cause ulceration and loss of tissue, or it may be an actual growth on
the affected area. Both forms cause inflammation and pain in the immediate area.
Diagnosis/Treatment: Biopsy and
histopathology are necessary for a diagnosis. Treatment of SCC may include
surgical removal of the cancer, cryotherapy, hyperthermia, or radiation therapy.
Amputation of the affected portion of the nose ("nosectomy") or ears
is usually required in nasal or aural SCC. The cosmetic result is often
surprisingly acceptable. Laser surgery is helping surgeons perform these
difficult surgeries, with a more rapid recovery period for the cat. Radiation
therapy may be helpful in many cases of feline SCC. In all cases, it is
important to avoid additional exposure to sunlight. Generally, this tumor type
is extremely aggressive in cats and may spread to local lymph nodes and attack
nearby bone, cartilage, muscle, or specialty organs such as the eyes and ears.
With aggressive treatment, many cats may live months to even years; however,
with advanced tumor growth, the prognosis becomes more guarded.
- Mast Cell Tumor:
Introduction: Mast cell tumors (MCTs) are the second or third most
common skin tumor in the cat. The average age at diagnosis is 10 years old,
although mast cell tumors have been seen in kittens. Male cats and Siamese cats
are more commonly affected with mast cell tumors.
Diagnosis/Treatment: This is one of the few tumor types that can be
diagnosed with a fine needle aspirate and cytology. Treatment depends on the
degree of involvement and nature of the cat. Surgery is usually considered the
best therapy, if feasible. Other possible treatments include laser surgery,
freeze-burning (cryotherapy), and electrotherapy to remove the tumors.
Antihistamines may also be used to help control the disease if it spreads
Introduction/Clinical Signs: Fibrosarcomas are aggressive, malignant
tumors that can occur anywhere on the body. They most commonly occur on the
limbs, ears, and trunk in cats. Feline leukemia virus can lead to fibrosarcoma
growth in young cats, usually occurring in multiple areas. Some fibrosarcomas
have also been found associated with giving certain vaccines. Fibrosarcomas are
usually irregular, firm, sometimes lumpy growths that often do not have distinct
borders. They generally grow rapidly and may ulcerate and drain at the surface.
About 20% of fibrosarcomas in cats may spread to other sites in the body.
is accomplished by histopathology. Cytology may help identify the typical
spindle-shaped cancer cells that make up fibrosarcomas, but large areas of
hemorrhage and tissue death commonly found inside the tumors may yield confusing
cytology results. Feline leukemia virus screening should be performed in all
cats with fibrosarcoma, especially if there is more than one tumor present.
Treatment begins with aggressive surgical removal. Radiation therapy,
chemotherapy, and cryotherapy may be helpful in some cases. Based on factors
such as location on the body and how much cell division is seen upon microscopic
examination, a prognosis can be given. Unfortunately, prognosis is poor in many
Avoiding infection with feline leukemia virus is probably the best form of
prevention available. Keeping only 1-2 cats per household, retaining cats
strictly indoors, and adequate vaccination protection all help in avoiding
exposure to FeLV. Unfortunately, the vaccine that protects against FeLV has been
known to cause some fibrosarcoma growths. Tumors caused by vaccines are
discussed in the next topic.
Introduction/Clinical Signs: Tumors that arise directly as a result of
vaccine administration are called postvaccinal sarcomas, vaccinomas, or
vaccinosarcomas. The number of cats that develop these potentially devastating
tumors following vaccination is on the rise, currently affecting between 1-10
cats per 10,000 vaccinated pets. These tumors develop with more frequency in
association with the following:
The tumor that results is very large, fast-growing and aggressive. They
always occur at the site of vaccination in the cat. The tumors are irregular,
firm, and usually attack underlying tissues to the point that they feel
continuous with muscle, bone, or other underlying tissues.
- Feline leukemia vaccines and certain rabies vaccines.
- Vaccines that are coupled with adjuvants (carriers such as aluminum,
which aid in the function of the vaccine).
- Repeatedly giving vaccines in the same spot on the cat.
Diagnosis/Treatment: Inflammatory lumps that occur following
vaccination are very common in both dogs and cats and should go away on their
own within 1-3 months. Any lump that remains in a cat beyond this time or is
obviously still getting larger after 1 month, should be examined by a
veterinarian. Biopsy/removal of the lump should be performed if there is any
question as to its nature. Histopathology will diagnose the condition. Most
post-vaccinal sarcomas are fibrosarcomas (connective tissue-origin cancer) (see
F770). Other types of tumors that may develop following vaccination
include liposarcoma (fatty tissue-origin cancer), osteosarcoma (bone-origin
cancer), rhabdomyosarcoma (skeletal muscle-origin cancer), and chondrosarcoma
(cartilage-origin cancer). The type of tumor that develops depends on what local
tissue responded with cancerous growth to the vaccine. Treatment is often
difficult. Surgery alone usually is unsuccessful. Radiation therapy is a very
helpful treatment tool for post-vaccinal sarcomas and may be combined with very
aggressive surgery for the best results. The prognosis usually remains guarded
even with the best treatment available.
Prevention: Avoiding vaccines altogether is the best prevention
technique available. However, the benefits of choosing to not vaccinate a cat
may not outweigh the risks. Any cat that has access to the outdoors and possible
exposure to other cats has a far greater risk of being exposed to feline
leukemia virus than it would have of developing post-vaccinal sarcoma. Since
feline leukemia virus is usually even more devastating and harmful than the
sarcoma, the risks of viral infection must be taken into consideration. Some
cats in certain situations may be at a low-enough risk to consider foregoing a
regular feline leukemia vaccine program— this decision should be made by the
owner with the help of a veterinarian. Rabies infection is fairly unlikely in
most cats (particularly those kept indoors); however, local law usually mandates
that cats be kept updated on rabies vaccine status. A new vaccine by Merial
called PureVax offers protection against rabies for cats without the use of an
adjuvant and has been shown to minimize vaccine-related reactions.
When giving feline leukemia and feline rabies vaccines, it is recommended
that they be given in a limb for the following two reasons: First, if a
vaccine-related tumor develops, the sparse tissues on a cat’s limb are less
likely to hide the problem, and it may be detected earlier. Secondly, in the
event that a tumor does develop, amputation of the limb may actually mean the
difference between life and death to the patient. Post-vaccinal sarcomas that
develop in the neck or back area do not give the treatment option of amputation
and are usually much more difficult to manage.
Introduction/Clinical Signs: Lipomas or fatty tumors are uncommon in
cats. They are benign growths, originating from fat cells (adipocytes).
Lipomas can be best diagnosed by histopathology. Cytology can be a useful
diagnostic tool as well; however, many tumors contain fat cells, and cytology
alone may lead to an incorrect diagnosis of a lipoma. The ideal treatment for
lipomas is surgical removal of the tumor. In overweight animals, a restricted
diet for some weeks prior to surgery may help reduce the size of the lipoma and
improve the surgeon’s ability to distinguish the tumor from surrounding
tissues. This will greatly reduce surgery time and increase the chances of
completely removing the tumor.
Sebaceous Gland Tumors:
Introduction/Clinical Signs: Sebaceous glands are found throughout the
skin of cats. Tumors of these glands can arise in cats, although they are
uncommon. Affected cats are usually older than 10 years of age, and the Persian
breed may be predisposed to developing theses tumors. The tumors are usually
isolated and occur on the head, neck, and body. They may look like warts, with a
pink/white cauliflower appearance.
Diagnosis: There are several
types of sebaceous gland tumors, most of which are benign. Diagnosis is by
histopathology, although clinical appearance and cytology may also establish a
fairly accurate diagnosis.
Proper treatment may include surgical removal, cryotherapy, or observation
without treatment. Malignant sebaceous gland tumors do occur and should be
removed surgically as soon as possible. However, these malignant tumors rarely
spread beyond the original tumor area.
Introduction/Clinical Signs: Papillomas, or warts, are uncommon in
cats. There are at least two papillomaviruses that are known to infect cats and
cause papillomas to grow. One infects the mouth (especially the tongue), and the
other infects the skin. Papillomavirus infection of the skin has also been
associated with the development of squamous cell carcinoma.
Diagnosis/Treatment: Histopathology is the diagnostic tool most often
utilized to establish a certain diagnosis; however, papillomas are often
diagnosed visually upon close inspection. Treatment of papillomas can include
surgical removal, cryotherapy, and observation (no treatment).
Introduction/Clinical Signs: Melanomas are tumors arising from pigmented
cells and are usually found as black, gray, or brown growths. In cats, they
occur most commonly on the ear, eyelids, lips, head, and neck. Malignant
melanomas may spread and cause aggressive destruction to internal organs.
Histopathology is the primary method of diagnosis. Melanomas may occur as benign
or malignant growths. Aggressive surgical removal of the tumor is the treatment
of choice, although spreading of the tumor may have already occurred at the time
of diagnosis. Radiation and chemotherapy have been used with varying success
Introduction/Clinical Signs: Hemangiomas of the skin are benign tumors
arising from the lining of small blood vessels. These tumors appear as well
defined, rounded, blue-black to red masses of varying firmness and size.
Hemangiosarcoma is the malignant and, unfortunately, more common cousin of the
hemangioma in cats. Hemangiosarcomas appear as blue/black to red plaques,
usually less than 2 centimeters in diameter, often with a bruised appearance.
Hemangiosarcomas usually occur in older male cats and commonly occur on the head
and face (occasionally on the paws). Long term exposure to sunlight may lead to
hemangioma and hemangiosarcoma formation in the head and tips of the ears of
Aggressive surgical removal is considered the therapy of choice; however, the
prognosis is guarded because spreading of the cancer to other areas in the body
can occur. Amputation is usually successful at curing hemangiosarcoma when it
occurs in the paws.
Introduction: Lymphoma is a malignant cancer of the lymphocytes.
(Lymphocytes are cells that help the immune system fight infection.) Any tissue
with lymphocytes can be affected, including the skin. There are several classes
of lymphoma, including a condition known as "mycosis fungoides." Years
ago a skin condition unlike most types of cancer was originally thought to be a
fungal infection. This condition has since been shown to be lymphoma in a form
that appears much like immune-mediated skin disease or a skin infection.
Although it is misleading because it implies a fungal infection, the name
"mycosis fungoides" has never been changed.
Clinical Signs: Lymphoma can appear as solitary or multiple skin
masses or plaques and may affect nearly any part of the skin. The nose, mouth,
footpads, and any haired or non-haired area of skin may be involved. Mycosis
fungoides can appear as reddened, itchy, scaly skin across large areas of the
body. It can also appear as ulcerations, crusting, swelling, irritation, and
loss of pigment around the nose, eyes, and lips, much like pemphigus.
Diagnosis/Treatment: The diagnosis of
lymphoma is made by biopsy and histopathology of affected areas. Prognosis for
cats with lymphoma of the skin is poor and is considered grave for cats with the
mycosis fungoides form. Surgical removal of the cancer in these cases is not
possible because such extensive areas of the body are usually involved.
Chemotherapy and different combinations of drugs are sometimes successful. For
lymphoma of the skin, the use of oral retinoids in cats has been tried with
Endocrine-Related Skin Disorders
Introduction: These are skin
abnormalities caused by problems with the organs that excrete hormones and
related substances. These disorders are encountered on a relatively regular
basis in cats. Three of the most common endocrine diseases affecting the skin
will be discussed:
- Hyperthyroidism: Hyperthyroidism and diabetes are the most common
endocrine abnormalities in cats, and both can lead to skin disease.
Approximately 1 in 3 cats with hyperthyroidism will suffer skin problems.
Matting of the haircoat, hair loss, excessive shedding, dry or greasy seborrhea,
thin skin, and secondary skin infections can occur in association with feline
hyperthyroidism. These skin problems usually resolve as the underlying endocrine
imbalance is properly treated. (See page F815 for a detailed discussion on
- Diabetes Mellitus: Secondary bacterial infections, dry skin with
dandruff (scale), thin skin, and hair loss are the most frequently seen skin
problems associated with diabetes mellitus. These abnormalities may or may not
be correctable through the proper treatment of diabetes. (See page F153 for
additional details on diabetes.)
Introduction/Clinical Signs: Hyperadrenocorticism, or Cushing’s
disease, is very rare in cats. Skin changes occur in about half of the cases.
Most commonly, cats develop thin, fragile skin that may tear easily. Hair is
sometimes lost, leading to partial or complete baldness of the trunk, abdomen,
or flanks. The skin tends to become thin and wrinkled, heals slowly from cuts
and scrapes, and bruises easily. Secondary skin infections (bacterial, fungal,
parasitic) are common.
Diagnosis: Since there have been so few documented cases in cats,
diagnosing Cushing’s disease in cats is more difficult than it is in the dog.
Generally, the ACTH stimulation test is used, along with dexamethasone
suppression tests and special testing of the urine.
Treatment: Most cats with Cushing’s disease also have diabetes
mellitus, thus complicating treatment. Treatment for most cats with Cushing’s
disease is also difficult because they are diagnosed when the disease is very
advanced. Medical treatment with mitotane, ketoconazole, and metyrapone have
been attempted, but none have been consistently helpful. Surgical removal of the
adrenal gland(s) is possibly the best option for affected cats. However, the
diabetes and skin fragility problems should be controlled first. Prognosis is
Miscellaneous Skin Disorders
Introduction: The term "seborrhea" is used to describe a defect
in production of sebum (normal skin oils), keratinization (normal growth and
turnover of skin cells), or a combination of both. Abnormalities can occur with
both quality and quantity of sebum. Generally, seborrhea is a secondary
condition seen in association with an underlying primary cause such as allergic
skin disease or endocrine-related skin disorders. Primary seborrhea does occur,
but it is uncommon.
Types of Seborrhea:
Treatment: The treatment of seborrhea focuses on treating or
correcting the underlying cause. Moisturizing shampoos/conditioners that contain
sulfur/salicylic acid are extremely helpful with seborrhea sicca (see page G750). Seborrhea oleosa can be managed with a de-greasing shampoo/conditioner
that contains benzoyl peroxide or coal tar (see page G659).
- Seborrhea sicca: Seborrhea sicca is thought to be a result of
decreased sebum/oil production leading to dry, dehydrated skin. The hair coat is
dull and the skin is dry with "scale" (white or gray flakes of dry
skin found in hair coat). Seborrhea sicca is the most common form of seborrhea
seen in cats.
- Seborrhea oleosa: With this problem, excessive sebum/oil production
in the skin causes a thick, greasy, sticky hair coat. This condition is usually
very messy and can emit a foul odor. Seborrhea oleosa is extremely rare in cats
and can indicate liver, pancreas, or intestinal disease. It may also be the
result of an abnormal reaction to a drug that is administered.
- Nutritional Skin Disorders: A number of nutritional deficiencies or excesses can
lead to skin disease. Notably among these are deficiencies of vitamins A, B, and
E, fatty acids, protein, and zinc. Excessive levels of vitamin A can also cause
- Vitamin A: Vitamin A is stored very well in the body. Excesses of
vitamin A can be seen in cats that are fed diets high in liver. Poor hair
coat, scaling (seborrhea sicca), hair loss, and secondary skin infections are
commonly seen. Diagnosis of this disease is usually made on historical and
physical examination findings. Treatment is alteration of the diet to
eliminate excessive vitamin A sources.
- Vitamin B: Vitamin B deficiencies often cause seborrhea sicca
with varying degrees of hair loss. Vitamin B is manufactured by bacteria found
in the intestine and is constantly absorbed over time. It is not stored in the
body, so vitamin B excesses do not occur. Any disease affecting the intestine’s
ability to absorb nutrients or affecting the population of bacteria found in
the intestine has the potential to result in vitamin B deficiency. Because it
affects the bacteria found in the digestive tract, prolonged antibiotic
therapy may also result in a vitamin B deficiency. Cats with chronic seborrhea
that has failed to respond to other treatments may respond positively to
vitamin B supplementation.
- Fatty acids: Fatty acid deficiency may be seen in cats fed only
dry, commercial foods that have been improperly preserved or stored. Cats that
are fed imbalanced homemade diets can also suffer from fatty acid deficiency.
Skin disorders resulting from fatty acid deficiency are seen several months
after starting the diet. Fatty acid deficiency leads to skin thickening,
seborrhea sicca, seborrhea oleosa, hair loss, and secondary skin infections.
Supplementation with essential fatty acid capsules or household oils (i.e.
corn oil, sunflower oil, or canola oil) may correct the problem, but it is
generally better to upgrade the diet to one of higher quality. Sometimes,
fatty acids are withheld purposely for certain medical conditions such as
pancreatitis and obesity. In these cases, the seborrhea and skin infections
may have to be treated without correcting the fatty acid deficiency.
- Vitamin E: Naturally occurring vitamin E deficiency is uncommon
in cats. Some cats fed exclusively high-fat diets do suffer from vitamin E
deficiency. Cats with vitamin E deficiency experience pain when handled in the
abdominal area, are irritable and listless, and may have a lack of appetite.
Death can occur if the condition is not corrected. Treatment consists of
dietary supplementation of a high-quality diet with vitamin E.
- Protein deficiency is unusual because most cat foods now
available contain adequate or even high protein levels. However, some diets
may be low in protein in order to treat another condition such as kidney
failure. Homemade vegetarian diets may also lead to protein deficiency in
cats. Protein deficiency leads to color changes in the hair coat (lightening
of darker hair), skin thickening, hyperpigmentation (darkening) of skin, and
patchy hair loss. The coat is brittle, dry, and rough. The changes are usually
symmetrical over the trunk, legs, head, and feet. Supplementation with protein
generally provides a good response.
- Zinc-responsive dermatosis: Dietary zinc deficiency has been seen
in kittens. Skin problems include hair loss, scaly, dry skin, and ulceration
of the lips. Treatment consists of proper supplementation of zinc in a high
quality kitten formula.