Common Allergies in Cats

An allergy is an unpleasant physical reaction caused by the cat's immune system overreacting to a food, something inhaled, or something in the cat's environment. Without an immune system, any animal would not be able to build up resistance to viruses, bacteria, foreign proteins, and other irritating substances that get into the system. Sometimes, however, the immune system reacts to things that aren't really a danger. Certain foods or substances such as pollens, powders, feathers, wool, house dust, and insect bites trigger a reaction typified by itching and sometimes sneezing, coughing, swelling of the eyelids, tearing, or vomiting and diarrhea. This reaction occurs in cats as well as in humans. In rare instances, the immune system reacts against the cells of the cat's own body-these are autoimmune problems.

For a cat to be allergic to something, exposure must occur at least twice. What the cat is allergic to is called the allergen. The way the body responds to that allergen is called a hypersensitivity reaction or an allergic reaction.

There are two kinds of hypersensitivity reactions. The immediate type occurs shortly after exposure and produces hives and itching. Hives in the cat are characterized by sudden swelling on the head, usually around the eyes and mouth, and occasionally the appearance of welts elsewhere on the body. The delayed reaction produces itching that occurs hours or days afterward. Flea bite dermatitis is an example of both types. This explains why a cat may continue to itch even after fleas have been removed from the cat and the environment.

Food Allergy

Cats may become allergic to certain foods or substances in foods. The most common food allergens are chicken, fish, corn, wheat, and soy; cats may also develop a food allergy to beef, pork, dairy products, or eggs. An intensely itchy rash often develops on the head, neck, and back, and may be accompanied by swollen eyelids. You may see hair loss and oozing sores from constant scratching. Sometimes, only the ears will be involved. In those cases, the ears will be very red and inflamed and may have a moist discharge. Less frequently, food allergy produces diarrhea or vomiting.

Treatment: Diagnosis is made by feeding the cat a diet without the suspected food for at least four to six weeks. The next step is exposing the cat to a suspected allergen and then watching to see if a reaction follows. There are numerous hypoallergenic diets available.

Atopic Dermatitis (Inhalant Allergy)

This is an allergic skin reaction caused by breathing pollens, house dust, molds, and other allergens indoors or outdoors. It may or may not occur seasonally. Signs and symptoms vary. They include itching on the head and neck, a rash along the neck and back similar to that described for feline miliary dermatitis, skin eruptions similar to those described in eosinophilic granuloma complex, and symmetrical hair loss over the body caused by excessive licking and grooming.

Atopic dermatitis is difficult to distinguish from other allergic skin disorders, such as those caused by insect bites, food hypersensitivity, and chemical contact. Diagnosis is best made by intradermal skin testing.

Treatment: Best results are obtained when the allergen can be identified and eliminated from the cat's environment. However, that is often not possible. Pollens, molds, and dusts can blow in through open windows and affect even indoor cats. Antihistamines or corticosteroids are beneficial in relieving symptoms but do not cure the problem. Allergy shots to hyposensitize the cat have been effective in some cases. Omega-3 fatty acids may also contribute to the cat's comfort and relieve some symptoms.