Atopy is a pruritic (itchy) skin disease of animals that is caused by an allergy to substances in the environment that are contacted through the air, either by absorption through the respiratory tract or contact through the skin. Atopy is thought to be an inherited disease. It can be difficult to diagnose in cats and, therefore, is probably under-diagnosed.

Symptoms of atopy usually begin relatively early in life, often by one year of age. Symptoms usually are seasonal at first, with most cats showing clinical signs in the summer months when airborne allergens (such as plant pollens) are present in higher concentrations. As atopic cats age, their symptoms tend to become less seasonal as they become allergic to more substances. Eventually, their itchiness can occur year-round.

Cats with atopy are usually itchy, particularly the hands and feet. The skin may be red and irritated due to scratching, and the ears may also be inflamed. The symptoms of food allergy are difficult to distinguish from those of atopy.

What to Watch For

Chewing at the paws

Scratching the face or rubbing it on the ground or with the paws

Scratching the ears

Shaking the head

Veterinary Care

Diagnostic tests are necessary to rule out other skin diseases, as well as to support the diagnosis of atopy. These tests may include:

A complete medical history and perform a thorough physical examination, especially checking the ears and the skin of the face and paws. Often, abnormalities may not be detected on the physical examination of cats with atopy. Occasionally, redness between the toes or around the muzzle of the face is the only finding.

Skin scrapings to eliminate other diagnoses such as demodectic or sarcoptic mange (caused by mites).

Fungal culture to rule out ringworm (also called dermatophytosis).

Skin testing (or occasionally blood testing) to determine specific allergens to which your pet may be allergic.

Initial treatments may alleviate symptoms, but do not treat the underlying cause of the allergy. Immunotherapy (allergy shots that work by modifying your cat's immune response to allergens) is considered the best treatment for moderate to severe or long-standing cases of atopy.

Treatments may include one or more of the following:

Antihistamines

Fatty acid supplements

Antibiotics to treat secondary pyoderma (bacterial infection of the skin)

Soothing shampoos

Corticosteroids (hormones) such as prednisone (very effective for reducing the symptoms of atopy, but have many potential side effects that can limit their long-term use).

NOTE: All of the above treatments alleviate symptoms, but do nothing to treat the underlying allergy.

For treatment of the underlying allergy:

Immunotherapy (allergy shots that work by modifying your cat's immune response to allergens; considered the best treatment for moderate to severe cases).

Home Care

Atopy cannot be cured and most cats require some form of therapy throughout their lives. You will need to administer any medications prescribed by your veterinarian and avoid offending allergens as much as possible. Skin testing (also called allergy testing) can be performed to identify the specific substances to which your cat is allergic. As time goes by, however, most cats with atopy become allergic to more and more allergens, making avoidance impractical in the long run.

You should practice strict flea control. Other itchy (pruritic) skin diseases such as flea allergy dermatitis may have an additive effect on your cat's skin condition.

Observe your cat for rashes and worsening of any skin lesions. Secondary bacterial infection of the skin (pyoderma) is common in cats with atopy and can contribute to their discomfort.

Preventative Care

Since enviromental exposure to allergens is important in the development of disease, it cannot be prevented. Airborne allergens, such as plant pollens, are difficult to avoid, and there is little that can be done to prevent the development of atopy in a predisposed individual. Cats that grow up in low allergen environments (dry climate with high elevation) may be less likely to develop symptoms.