Atopic dermatitis (also called atopy) is an allergy to substances from the environment. Substances that can elicit such allergic reactions are called allergens or antigens.
Atopic dermatitis is a common problem in dogs and cats, although dogs are more likely to have it than cats. A genetic basis is suspected since it occurs more commonly in certain breeds and lines. Allergen that are well-recognized triggers for atopic dermatitis include pollens, molds, dander (shed skin cells), house dust, tobacco smoke, and a variety of other substances.
The primary symptom of atopic dermatitis is itching, and the problem typically first becomes apparent when a pet is between 6months and 3 years old.
Early symptoms in dogs may be mild and can include foot-licking, face-rubbing, ear problems, and scratching behind the elbows, all without any visible reason (no visible fleas, no plant material caught in the hair coat, etc.). The problem is often seasonal. As time goes on, the allergy worsens and more areas of the body become involved. Itching that at first occurred only seasonally may become present all year round.
Cats with atopic dermatitis can show several different types of skin problems. Some show hair loss on the abdomen (belly) and inner thighs or on the back. This hair loss is from over grooming (licking, chewing) due to itching. Others may scratch around the face and neck. A condition called miliary dermatitis may develop, where small crusts (scabs) can be felt through the hair coat on the surface of the skin. Eosinophilic granuloma complex is another manifestation of allergies in cats; signs include raised, flat, reddened areas (plaques) on the skin or sores on the upper lip.
Diagnosis of atopic dermatitis may be challenging because many other types of skin problems produce the same degree of scratching, hair loss, and redness of the skin. For your veterinarian to reaching the conclusion that atopic dermatitis is present (i.e.,establishing the diagnosis), a combination of elements usually needs to be present:
- The typical history of the onset of itching (often seasonal, since pollens are a common cause of atopic dermatitis), plus
- Finding a typical pattern of skin lesions over affected areas, and
- The exclusion of other causes of itching.
Your veterinarian will use a thorough physical examination and often will need to perform several tests to rule out other skin problems such as mange mites, ringworm, bacterial infection, or flea allergy, any of which can cause itching and scratching that is identical in initial appearance to atopic dermatitis. Once the diagnosis of atopic dermatitis is made, treatment can be undertaken for comfort and relief of itchiness, or further tests can be conducted to determine which substances in the environment are triggering the atopic dermatitis in order to remove them or desensitize your pet to them as a part of treatment. These advanced tests include intradermal skin allergy tests and serum (blood) allergy tests.
Several approaches can be taken for treatment. The best option for the pet’s health is to perform tests to determine which allergens are causing the problem. Then, if possible, you can take steps to minimize or eliminate exposure to the allergens in your pet’s environment. If the allergens cannot be avoided (such as when pollens from plants or trees are the cause), a series of injections of small amounts of the allergens can be used for gradually causing desensitization to the allergen. It is also important to look for other problems that may be contributing to the itching.
Many pets with atopic dermatitis are “polyallergic” and also have other sorts of allergies such as food allergy or flea bite allergy. These allergies compound the symptoms of itching and scratching. Therefore, working with your veterinarian to determine whether your pet has an allergic disorder beyond atopic dermatitis can be important if your pet is allergic both to airborne allergens and fleas, certain food ingredients, or other trigger substances.
Skin that is inflamed due to scratching and chewing from atopic dermatitis is prone to bacterial or yeast infections that can themselves also cause even more itching. A simple sampling off the surface of the skin (skin scraping) and examination of the harvested skin cells under a microscope can identify whether these complications exist; antibiotic or anti-yeast treatment can make an enormous difference in such cases.
Finally, long-term and/or high-dose treatment with cortisone-like medications may limit the skin’s natural defenses and allow opportunistic infections, such as sarcoptic mange, to develop. This, too, causes more itching and scratching; the simple skin scraping procedure described above is the test of choice for identifying sarcoptic mange when it is present, and elimination of sarcoptic mange is straightforward and highly effective.
Therefore, elimination of as many causes of itching as possible (e.g., fleas, food allergies, secondary skin infections) can control a pet’s symptoms, even if the atopic dermatitis itself is not treated. Consult your veterinarian on carrying out these steps and also to have your pet checked for skin infections.
Several medications are used for treating itching caused by atopic dermatitis or allergies in general. Antihistamines are helpful in some pets. Omega-3 fatty acids can help ease skin inflammation. Corticosteroids (cortisone-like medications) are often used for reducing inflammation and itching, and are usually very effective. However, corticosteroids are powerful medications that can have serious side effects when used long term, so they should be used at the lowest dose possible and for as limited an amount of time as possible, or on an intermittent, as-needed basis. Cyclosporine is a powerful immunosuppressive medication that has been approved for the treatment of itching caused by atopic dermatitis in dogs. It works as well as corticosteroids in controlling itching and produces far fewer side-effects, but is more expensive.