Atopy Or Atopic Dermatitis In Dogs

Atopy, Atopic Dermatitis, or Allergic Inhalant Dermatitis is a condition affecting 10% of dogs.

Atopy is very much like hayfever in people. Both species inhale pollen, dust, molds, house dust mites or other allergens, then have an allergic reaction.

The difference is what dermatologists call the “shock organ,” or reactive part of the body. In people, the shock organ is the respiratory tract, so people tend to have runny noses, coughing, sneezing and sinus infections.

Dogs, instead, react with the skin, and typically the front of the body is affected most. Classic evidence of atopy is itchiness in the face, ears, feet, axillae (armpits) and down the front of the front legs.

There are known to be 64 allergens that dogs can inhale and have an allergic reaction to.

Dogs who have ear infections early in life are likely to become atopic later. Average onset of signs is 3-5 years of age, although I have seen puppies as young as 12 weeks with atopy and dogs as old as 14 years having their first episode.

Many dogs affected with Allergic Inhalant Dermatitis can be observed rubbing their faces in the carpet or pawing at their snouts. Eyelids may be inflamed, moist and even hairless. Roll the dog over and you are likely to see the axillary region inflamed and hairless.

Patients with chronic atopy and itchy feet may have dermatitis between the toes, top and bottom. Deep bacterial infection from long-term moistness will add to the itchiness. These infections are often characterized by highly resistant organisms. The syndrome is known as pododermatitis. Broken down the Latin prefix “podo” means “foot,” “derma” means “skin” and “itis” means “inflammation.”

Infection in other areas of the body is another common sequella of Allergic Inhalant Dermatitis. Here it is called pyoderma. Pyoderma affects the pores and hair follicles of the skin and, like infection in pododermatitis, adds to the itchiness. Long-term antibiotic therapy is needed for pyoderma and it is not unusual to treat these patients for months at a time. Convenia is effective in many cases, and is especially helpful in those patients who are difficult to pill.

In most cases pyoderma also needs to be addressed topically with shampoo therapy. Frequent shampooing has the added advantage of removing allergens little dustmop dogs pick up in the course of their everyday activities.

Other aspects of treatment of atopic dermatitis in dogs include oral medications that can include antihistamines such as diphenhydramine (Benadryl) and Hydroxyzine. Diphenhydramine is of limited value in most dogs. Its most-pronounced effect in people, drowsiness, can be dramatic in dogs, while its ability to control itchiness in the species is very limited.  Hydroxyzine is commonly used for atopy. It is safe, highly effective and reasonably-priced.

Oral and/or injectable corticosteroids can play a part in short- and long-term treatment of atopic dogs.

Another method of oral therapy is Atopica, by Novartis Animal Health. Atopica: is a cyclosporine product FDA-approved for use in this condition, and effective in many cases.

Another form of treatment is commonly referred to by laymen as “allergy shots,” although the correct term is hyposensitization. The Latin prefix “hypo” means low or below, so the process decreases sensitivity. In other words, the immune system, which is reacting inappropriately to pollen, dust and molds, is “told” to back off in its reaction.

The process involves giving injections of the very things the patient is allergic to. In doing so, the immune system is “taught” to react less and less to the offending allergens.

There are two ways to get to the point of hyposensitization injections.

Board-certified veterinary dermatologists can perform skin testing. The technique is similar to patch testing that is done on people. Instead of allergens being under patches, tiny amounts of allergens are injected into multiple places to allow the dermatologist to “read” the reactions to the injections and determine which allergens are offensive to an individual pet. That report is sent to a laboratory, which makes hyposensitization solution specific for the individual pet tested.

In vitro testing begins with a blood sample, which is sent to a laboratory that tests for evidence of reactions to various allergens. In vitro testing may be performed by any veterinarian. The evidence is in the form of antibodies, proteins the immune system has created that are specific for the body’s reaction to each different type of allergen. The same company that determines which allergens’ antibodies are present also makes the hyposensitization solution for the patient.

Either the dermatologist or the primary care veterinarian teaches the pet owner how to give the injections, which are continued for a lifetime. If, at some point, the patient ceases to be under control, testing may be repeated to see if new allergies have developed.

Atopy is a condition that must be constantly monitored, but can be controlled in virtually every patient. Unlike some allergies in children, however, it does not go away, and treatment will be required for a lifetime.
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