A cat with an allergic reaction around its eyes.

What Is Atopy in Cats?

Atopy is a type I hypersensitivity reaction that causes itching in cats. It is associated with the presence of skin-fixed or circulating immunoglobulin E (IgE) that is specific to environmental allergies. Feline atopy has also been called non-flea, non-food allergic dermatitis.

Atopy is caused by an allergy to airborne substances in the environment, either by absorption through the respiratory tract or contact with the skin. It is thought to be an inherited disease, and is the second most common type of dermatitis in cats, following flea allergy dermatitis. Atopic dermatitis has also been documented in humans and dogs. Allergens that trigger this disease can be both indoor and outdoor, and seasonality can provoke clinical signs based on the inciting allergen and exposure.

Symptoms of atopy usually begin relatively early in life, often by one year of age. They’re usually 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 and more specific to certain substances. Eventually, their itchiness can occur year-round.

Symptoms of Atopic Dermatitis

Cats that suffer from atopic dermatitis tend to be pruritic (itchy) and will often over-groom their hair coat, legs, and paws. Their skin may be red and irritated due to scratching and self trauma.

Clinical signs of atopic dermatitis are very similar to other forms of dermatitis in cats. Miliary dermatitis is a term that describes the pattern of lesions that some cats get with atopic dermatitis. This pattern isn’t seen in dogs or humans with atopy. Miliary dermatitis can also be seen with flea and food allergies, since they’re a manifestation of allergies in cats, as opposed to being a distinct form of atopy.

Clinical signs include:

Diagnosis of Feline Atopic Dermatitis

Atopic dermatitis looks similar to other types of dermatitis (like mange, ringworm, and pemphigus foliaceus), therefore, your veterinarian will need to examine your pet, rule out other diseases, and isolate the diagnosis.

Diagnosis of atopic dermatitis often includes:

Treatment of Feline Atopy

Two primary forms of treatment for atopy are drug treatment and immunotherapy. The ideal treatment for most moderately and severely-affected animals is some combination of both types.

Drug therapy relieves the symptoms of atopy, but does not treat the underlying allergy itself. Most cats with atopy are young, and may require years of therapy.

Drug treatments for atopy include:


Immunotherapy (like hyposensitization, desensitization, and allergy shots) is the ideal form of treatment for atopy, and is recommended for cats that cannot be managed safely and effectively with symptomatic therapy. The exact mechanism by which immunotherapy works is not well understood, but the goal is to induce tolerance to allergens through the immune system. This technique is effective in 60 to 80% of atopic cats.

Initially, an extract of the allergens selected by allergy testing is prepared. A small amount is injected every 1 to 2 days, with the dosage gradually increasing. Due to the frequency of injections, your veterinarian will show you how to administer the injections at home. Once the cumulative dose reaches a certain level, the injection interval is slowly increased until injections are given every 2 to 3 weeks. The interval may then be maintained for a relatively long period of time. Improvement is gradual and your cat may not benefit markedly for the first 3 to 6 months of immunotherapy. Antihistamines, fatty acid supplements, and soothing shampoos may be used while immunologic tolerance develops.

Home Care

Atopy is incurable 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. 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 pruritic skin diseases, such as flea allergy dermatitis, may have an additive effect on your cat’s skin condition. Year-round topical flea and tick preventative medication is imperative for all cats (even indoor-only pets).

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.

Follow-Up Care for Cats with Atopy

Atopy varies considerably in intensity based on the individual animal and its environment. Therefore, home monitoring and close communication with your veterinarian are vital for success. Treatment is effective if individualized to the patient.

Follow-up for atopy may include the following:

Cats with seasonal atopy may not require medication during certain parts of the year. Close observation and good record-keeping may identify times when medications are not needed.

In-Depth Information on Diseases that Mimic Atopy

Itching is a symptom in many feline skin diseases, which may lead you to believe that your cat suffers from atopy. Ruling out other causes of pruritus is an important part of establishing a diagnosis.

Diseases that mimic atopy in appearance include: