Ask the Vet: Atopic dermatitis, Part 1

Ask the Vet: Atopic dermatitis, Part 1

Allergens are classified into four major categories in veterinary medicine: pollens, mold spores, dander and dust mites. Stock photo
Getting to the source of the itch

By Matthew Kearns, DVM

I expect at some point there will no longer be any snow on the ground. Once that happens I will truly suffer with burning eyes, runny nose, sore throat and an intermittent cough. Ugh, my wretched seasonal allergies are back!! 

Well, just like us, pets can also suffer from seasonal allergies. Pets can suffer from all of the signs I mentioned above but, most commonly, they suffer from itchy feet, recurrent ear infections and rashes all over the body. 

This phenomenon of seasonal allergies is known as atopy, or atopic dermatitis. Dermatitis stands for “inflammation of the skin,” or a rash. Atopy is defined as “a genetic predisposition to develop allergies to allergens” (proteins in the environment). Atopy and atopic dermatitis hiccup in the immune system. 

The immune system produces immunoglobulins (Ig), or antibodies, to protect us against infections and parasites. There are five major classes of immunoglobulins: IgA, IgD, IgE, IgG and IgM. These antibodies work with white blood cells to trigger the release of cytokines. Cytokines are chemicals that fight against/kill bacteria, viruses, fungal infections, parasites and even cancer cells. The antibody IgE is the antibody associated with allergies. IgE has a beneficial effect by protecting against certain parasites, particularly gut parasites. 

Unfortunately, these same IgE antibodies recognize allergens, or proteins associated with allergies, the same as parasites. This fools the immune system into producing more IgE antibodies that trigger a certain white blood cell called basophils into releasing large amounts of cytokines (particularly histamine) into the system. This release of histamine causes a systemic reaction that triggers inflammation of the skin all over the body. 

Allergens are classified into four major categories in veterinary medicine: pollens, mold spores, dander and dust mites. Each of these allergens is going to be in higher concentrations at different times of the year. Pollens are high when grasses, weeds, flowers and trees bloom, which is late spring/early summer through late fall. Mold spores are from decaying plant material and occur from late fall/early winter and late winter/early spring. Dander and dust mites are around in the cold winter with low humidity.  

We mentioned at the beginning of the article that pets can suffer from all the same symptoms of hay fever, but it is less common than skin rashes and ear infections. Why is that? Those same allergens that are in the air also land on the ground, and research has found pets that suffer from atopic dermatitis are triggered by percutaneous (through the skin) absorption. 

These pets have defects in the lining of their skin so the allergens are literally absorbed through their feet and other areas where the skin is exposed (stomach, face). Many times if we see pets that have a severe pododermatitis (inflammation and infection of the skin on the feet) that is a clue that atopy or a seasonal allergy is afoot (no pun intended). Once we diagnosis atopic dermatitis we next need to treat it. We will discuss how to treat this condition in my next article.

Dr. Kearns practices veterinary medicine from his Port Jefferson office and is pictured with his son Matthew and his dog Jasmine.