By Arnold Plotnick, MS, DVM, ACVIM
Skin Disorders in Cats
Veterinarians have wryly observed that months can go by without seeing a particular disorder in their veterinary practice, and then suddenly: three in a row. It’s uncanny. I experienced this phenomenon on a recent Saturday in my own New York City cat practice, where our clinic was transformed into the set of a new daytime soap opera: The Bald and the Beautiful. Figaro, Poousch, and Decaf – three cats with balding bellies and hairless hides.
Feline skin disorders are a diagnostic challenge. While there are many distinct feline skin disorders, they all may present with similar clinical signs, although certain “reaction patterns” are more common in some disorders compared to others. Examples of some common reaction patterns seen in feline dermatology are hair loss (alopecia) and small widespread scabs and crusts (miliary dermatitis).
Baldness may be okay for Sphynx cats, Chinese crested dogs, and George Costanza. For many cats, however, it may be a sign of allergy, parasites, or infection. Quite often, a psychological disorder is triggering the hair loss.
Hair loss in cats should be investigated by a veterinarian, where careful questioning and examination will determine whether the hair is falling out, or if the cat is chewing the hair or yanking it out through over-grooming. Clients may actually report to the vet that the cat is grooming herself excessively, and that hairballs have become increasingly difficult to control. Finding broken hairs during the exam confirms that the cat is chewing at its fur. Successful treatment will depend on the cause of the hair loss.
Allergies are a common reason why cats over-groom and pull out their fur. Flea allergy, food allergy, and atopy (allergy to airborne substances) are three common causes of allergy in cats. Flea allergy is suspected if fleas or flea dirt is noted during the exam. Even if fleas are absent, flea allergy can be involved. Fleas deposit their saliva into a cats skin before they draw their blood meal, and flea-allergic cats may show a severe reaction to the saliva, even from one flea bite. The itching can be intense, and cats may lick and chew excessively at their skin, especially around the base of their tail.
Adverse reactions to food may manifest themselves via the skin. Severe generalized itching, small scabs and crusts throughout the haircoat (called “miliary dermatitis”), itching around the head, neck, ears and face, and self-inflicted hair loss due to over-grooming may be seen. Blood tests and intradermal skin tests are available, however, these are generally considered unreliable for the diagnosis of food allergy. Dietary elimination trials, in which the cat is fed a diet containing a protein source they haven’t encountered before (such as duck, rabbit, or venison) are necessary to obtain a definitive diagnosis. These trials require patience on the part of the owner, as it may take anywhere from 3 to 8 weeks before improvement is noted.
Allergies to airborne substances (called “atopy”) such as pollens or dust can lead to itching and subsequent excessive grooming and hair loss. Miliary dermatitis is another common manifestation of atopy. Achieving a diagnosis can be tricky.
Clinical signs that are seasonal are suggestive of atopy, although signs can be seen all year round as well. Blood tests can be performed to see if the cat is allergic to plants indigenous to a particular geographic region as well as to common household dusts and mites, although some dermatologists still feel the blood tests to be unreliable. Intradermal skin testing, in which tiny amounts of allergenic substances are injected into the skin and the skin reaction noted, is a more meaningful diagnostic test. This should be performed by an experienced veterinary dermatologist, however, as the skin response to the injections can be subtle and more difficult to interpret in cats. Specific treatment of an allergy is possible if the allergen(s) can be identified and avoided or removed from the environment. Often, this is not practical, especially in patients allergic to airborne pollens. Hyposensitization – serial injections of progressively larger amounts of the offending allergen – is probably the most appropriate long-term control method for cats with a prolonged allergy season. Other therapies that can be considered are anti-histamines, omega-3 fatty acids, and corticosteroids. Although steroids have the potential to have side effects, the doses necessary to control allergic dermatitis are unlikely to cause problems, especially in cats, as cats are more resistant to the undesirable side effects of steroids as compared to dogs.
Ringworm is a skin fungus that may cause hair loss. It is the most common infectious skin disease in cats. Any age, sex, or breed of cat may be affected, although young cats, older cats, and longhaired cats are more frequently affected. The fungus invades the hair shafts, and hair loss results. Some cats with ringworm infection are very itchy, while others don’t seem to be bothered by it. Most cats develop scaling, crusting, and redness at the sites of infection. Some cats will over-groom and develop hair loss. Ringworm infection should be considered in any cat with symmetrical hair loss. Ringworm is a “zoonotic” disease – it can be transmitted to humans. When clients present their cat with a classic circular crusty skin rash, and they themselves have a similar rash, you can be almost certain that ringworm is the culprit. A definitive diagnosis, however, is achieved through fungal culture. Treatment options vary, depending on the situation (an individual cat vs. cattery or multiple cat household, longhaired cats vs. shorthaired cats), but may involve some combination of clipping the coat, topical therapy (usually shampooing), oral medication, and environmental decontamination. Treatment is often successful if clients are diligent about following the prescribed protocols.
Once parasites, allergies, and other medical problems have been ruled out, psychogenic alopecia – hair chewing and overgrooming due to psychological factors such as stress, fear, anxiety, or nervousness – must be considered. Cats are very sensitive to their environments, and a move to a new home, addition or subtraction of new people or animals to the household, or any other unexpected change to their surroundings can provoke grooming behavior that is excessive, leading to hair loss. Grooming is a comfort behavior, often used by cats to relax themselves. It shouldn’t be surprising that in the face of stress or anxiety, they may turn to excessive grooming to dispel their anxiety. Cats of Asian lineage (Siamese, Abyssinians, Burmese and Himalayans) are apparently more susceptible to psychogenic alopecia, presumably because of their high-strung, nervous temperaments.
After a thorough medical exam and diagnostic testing, all three cats that came in to my practice that Saturday – Figaro, Poousch, and Decaf – were eventually diagnosed with psychogenic alopecia. Figaro’s case was the most clearcut. His hair loss began as soon as Ernie (another cat) was added to the household. All three cats had licked the fur off their abdomens and inside their thighs. Figaro’s over-grooming had progressed to his tail, while Poousch and Decaf were also chewing the hair off their forearms.
Ideally, the treatment of psychogenic alopecia would involve the elimination of the potential stressors in the cat’s environment. Unfortunately, this is often impossible, and anti-anxiety or anti-depressant medications are often warranted to control the problem. Psychogenic alopecia is a diagnosis of exclusion. When all of the common causes of hair loss have been ruled out, we attribute the hair loss to psychogenic factors. Anti-anxiety medications shouldn’t be relied upon as the sole treatment; behavior modification is also an important part of the treatment plan.