The term “allergy” is a general reference to an immune-mediated hypersensitivity reaction to some antagonizing environmental “allergen,” which is normally innocuous to non-allergic animals. A more specific definition of “allergy” is an altered reaction to something (the allergen) following a second or subsequent exposure to it. Virtually anything in the environment can be an allergen.
How Skin Allergies Affect Cats
Once a cat has been exposed to an allergen, subsequent exposure to the same substance will cause hypersensitivity (allergic) reactions, depending upon the particular cat’s immune make-up. Most allergic reactions in cats cause some degree of skin irritation; the skin becomes inflamed, severely itchy (pruritic), irritated and red. Owners often report rashes, licking, scratching, biting, restlessness, pustules or bumps on the skin, “hot spots” where the skin becomes raw and infected from self-trauma, sneezing, red watery eyes, excessive grooming and generalized lethargy. Cats seem to be most commonly affected in the groin or flank area, on the paws, between the toes, in the ears, in the axial area (armpits) and under the neck. Secondary bacterial and yeast infections often occur, especially in the ears, accompanied by a foul, yeasty odor. Cats with food allergies can have gastrointestinal disturbances in addition to skin irritation, such as burping, vomiting, diarrhea, flatulence (excessive production of intestinal gas), weight loss, hives and enlarged lymph nodes.
Depending upon the inciting cause, allergic cats usually begin to develop clinical signs before the age of two. These signs are often seasonal and may disappear in the winter, only to return with a vengeance during hotter months of the year.
Causes of Feline Skin Allergies
Most feline allergies are hypersensitivity reactions to flea or tick bites, contact or airborne inhalants or some ingredient in their food. The inciting contact with the allergen can be by touch, inhalation, injection or ingestion. Allergies to fleas, which are quite common in cats, are caused by an immune-mediated hypersensitivity reaction to flea saliva, which leads to irritation and itchiness at the site of a bite, increasing the risk of secondary bacterial infection and localized hair loss. Common contact and inhalant allergens include seasonal pollen, trees, bushes, grasses, weeds and flowers. These allergies, in cats and in people, are sometimes referred to as “hay fever.” Food allergies can be a reaction to essentially anything in a cat’s diet. Some common food allergens include beef, dairy products, wheat, eggs, chicken, lamb and soy. Cats also can develop allergies to indoor or outdoor mold spores, dust mites, household cleaners and chemicals, drugs or a number of other environmental allergens.
Why some cats are so terribly affected by skin allergies while others are not is unclear. There seems to be a genetic predisposition to developing allergies, since the condition often occurs in littermates or in the offspring of cats that suffer from allergies. Skin allergies may also be linked to stress or systemic medical disorders. Cats that are particularly anxious or fearful may be prone to developing skin allergies, and cats that are in poor health may also succumb to skin allergies more easily.
Preventing Allergies in Cats
The best way to prevent allergic reactions in companion cats is to prevent their contact with (or inhalation or ingestion of) whatever is causing the hypersensitivity. For example, flea bite allergies are best prevented by removing the allergen – fleas – from the cat’s environment. There are a number of good topical products to keep fleas off of our pets, including medicated collars and topical liquid treatments and preventatives, among others. To prevent hay fever, owners should keep their affected cats away from whatever seasonal allergen is causing the problem. Food allergies can be prevented once the causative dietary component is identified, which can be done through an elimination diet supervised by a veterinarian. A number of commercial kibbles containing novel protein sources are available for cats that are allergic to more traditional protein sources.
Feline skin allergies can be difficult, but not impossible, to diagnose and manage. Veterinarians use a combination of a thorough medical history, comprehensive physical examination, blood and/or skin tests and assessment of the cat’s response to treatment to identify and control allergic reactions. Cats with skin allergies have a variable prognosis – again, depending upon the underlying cause of the condition. In many cases, the allergies will resolve with effective flea/parasite control, special diets and/or medicated topical treatments. Unfortunately, sometimes the precise cause of the allergy remains elusive.