Allergic Skin Disease

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My pet has itchy skin and ears. What could this mean?

Itchiness and ear infections in dogs and cats are most commonly caused by allergies, either to fleas, environmental allergens, or food (or a combination of these factors). Allergies can cause secondary bacterial or yeast skin infections, which can make your pet even more itchy. The goal in managing any allergic skin disease is to manage the underlying allergy and to treat secondary infections.

 

What are some common allergies?

FLEA ALLERGY DERMATITIS: Flea allergy is the most common type of allergy, especially in San Francisco. Dogs and cats can develop an allergy to the saliva of the flea, and even one bite can set off an allergic reaction in sensitive animals. Minimal exposure to fleas is all that is needed. This means you may never see evidence of fleas, yet the exposure is enough to cause allergies. The goal in managing flea allergy dermatitis is minimizing flea exposure, which requires more frequent (every 2 – 4 weeks) administration of topical treatments (such as Frontline, Advantage, or Revolution), with newer oral products (such as Capstar or Comfortis), or a combination of both.

 

ATOPIC DERMATITIS (environmental allergies): This is an allergic reaction to allergens in the environment (such as house dust mites, pollen, or grasses). The allergens are either inhaled or come in direct contact with skin. Regular flea preventatives and diet are also very important, as any additional antigenic stimulation can make atopic allergies worse.

 

FOOD ALLERGY DERMATITIS: This is the least common type of allergy in dogs and cats. The most common allergens are protein sources (such as chicken, beef, and dairy) and pets can develop an allergy to a food they have been eating for some time. Some pets will also have gastrointestinal signs (vomiting or diarrhea). There is no effective blood or skin test for food allergies; the only way to diagnose a food allergy is by feeding a novel protein or hypoallergenic diet for 8 – 12 weeks while observing the pet to determine whether they are less itchy. The hypoallergenic diet does need to be exclusive, especially during the trial period.

 

How are allergies treated?

Regardless of the cause of the allergy, suppressing the allergic response can make a pet more comfortable and less itchy. The most effective therapy is some form of steroid, like prednisone. Sometimes a short course of steroids is sufficient to break a temporary allergic cycle. Other patients require longer courses of steroids to keep their itchiness under control. Common side effects of corticosteroids include increased thirst, appetite, and urination. While more serious side effects are also possible, all of the side effects are dose dependent. Especially when combined with other therapies and good flea control, it is common to be able to find a dose of steroids that is effective, with minimal side effects. Topical steroids can be very effective for focal or ear allergies, with less side effects.

 

Other management options for allergic dermatitis include antihistamines, immunosuppression therapy (such as cyclosporine), fish oil/omega-3 supplementation, frequent bathing with special shampoos, hyposensitization injections, and controlling any secondary infections. These are longer term strategies and their real objectives are to reduce dependence on long term steroids.