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Canine Atopic Dermatitis

Carol S. Foil, DVM, MS, Diplomate A.C.V.D.
Board-certified specialist through the American College of Veterinary Dermatology

Canine atopic dermatitis (allergic dermatitis, canine atopy) is an inherited predisposition to develop allergic symptoms following repeated exposure to some otherwise harmless substance, an "allergen," such as dust mites or pollen. Most dogs begin to show their allergic signs between 1 and 3 years of age. Due to the hereditary nature of the disease, several breeds, including golden retrievers, most terriers, Irish setters, Lhasa apsos, Dalmatians, bulldogs and Old English sheep dogs are more commonly atopic, but many dogs, including mixed breed dogs can have atopic dermatitis. The incidence is increasing both in man and animals.

Atopic animals will usually rub, lick, chew, bite or scratch at their feet, muzzle, ears, armpits or groin, causing hair loss, and reddening and thickening of the skin. In some cases several skin problems can "add" together to cause an animal to itch where just the allergy alone would not be enough to cause itching. These problems include air borne-allergens (pollens, etc.), allergens in food, and allergens from parasites (fleas, etc.) and also bacterial or yeast infections of the skin. Eliminating some but not all of the problems may allow a patient's itchiness to go away. Therefore it is important to treat any other problems that could be making your pet itch while dealing with allergy.

Diagnosis

Specific diagnosis of atopic dermatitis is based upon the results of intradermal testing and/or in vitro (blood) testing. Many medications can interfere with our ability to properly skin test your pet. Length of time that a medication's effect remain in an animal's body is highly variable; however, basic guidelines for withdrawal of medications are: At least 4 weeks off oral prednisone; 10 weeks after triamcinolone acetonide injection; 14 weeks after methylprednisolone acetate injection; 10 to 14 days off antihistamines; 10 to 14 days off topical steroids (ear drops, ear drops or medication for skin); 2 days off tranquilizers.

Treatment

1) Antihistamines: This medication works in 20% of atopic patients. Your pet can take antihistamines for life. The only side effect usually seen is drowsiness. Several types may be tried to find the one best for your pet. Topical antihistamines for the eyes can be helpful in patients with eye allergy (itchy conjunctivitis). Visine A® is one over-the-counter product that can be helpful.

2) Avoidance of the allergens: This can be helpful for house dust mite allergies. Pollen exposure can be reduced by using air-conditioning and air filters, avoiding the outside early morning and late afternoon, wiping down with moist cloths after going outside and frequent bathing.

3) Oral Steroids (prednisone, cortisone, triamcinolone, etc.): These drugs have many potential side effects and are reserved for adult animals, those with short seasonal problems or where other therapy is not possible or is ineffective. Typically, treatment is started at one dose and then tapered off to every other day usage.

4) Topical Steroids: Topical usage is safer than oral usage. It can be very helpful if itching is localized (e.g., eyes, ears). It can be used for more widespread disease in the form of leave-on rinses or lotions (ResiCORT®) or a triamcinolone spray (Genesis®).

5) Cyclosporine (Neoral®): This immunosuppressive agent can be used at low doses to treat allergy successfully in about 60% of patients. It can also be used to lower needed dosages of steroids. The major short-term side effect is gastrointestinal upset. The long-term safety is not completely known. The dosage can often be lowered after a few weeks of successful treatment.

6) Tacrolimus (Protopic® ointment): This drug is related to cyclosporine. It can be very useful for treating localized itchy areas in atopic dermatitis. It is applied once or twice a day at first, and then frequency is reduced.

7) Fatty acid supplements: Certain types of oils can reduce allergic symptoms in some patients. We can give fish oil capsules in conjunction with a low-fat diet or prescribe special prescription diets with the fish oil content raised. This therapy can help improve response to antihistamine therapy.

8) Allergen Specific Immunotherapy: This involves giving an allergy vaccine injection that is made up specifically for your pet, usually for the lifetime of the animal. After an initial series of injections, periodic boosters will be needed (every 1-3 weeks). 60% to 80% of animals will improve with the vaccine. Results may not be seen for 3 to 6 months. When results are not seen in 9 to 12 months, a re-evaluation is necessary.

9) Bathing: Atopic skin is sensitive and subject to drying. Only specially designed hypoallergenic shampoos should be used on your allergic dog. Rinsing should be thorough. Generally it is best to follow with a hypoallergenic cream rinse or spray to remoisturize the skin after every bath. Virbac's Allermyl® comes as a shampoo or a spray and contains 1-rhamnose, which may reduce itch and inflammation.
 
Instructions For Your Pet

1. Topical Therapy:

A. Locally ____________________________________________________________
B. Whole body _________________________________________________________

2. Bathing Protocol:

Bath at least once a week with _________________.
Lather 5 minutes, rinse very well.
Follow with a spray or cream rinse (_______________) to rehydrate as indicated.

3. Systemic Therapy:

A. - Steroid therapy:

Give ____ mg once a day for _____ days,
then ______ mg once a day for ________,
then _______ mg every other day for _______days.

B. - Antihistamine therapy:

Give ______________, _____ mg once ____ or twice ____ a day, indefinitely.

C. - Cyclosporine therapy:

Give Atopica, ___ mg or ml, once ____ or twice ____ a day, with food.

4. Fatty Acid Therapy:

Give ______ capsules, daily with food or use _________ prescription diet.

By Dr. Carol S. Foil, DVM, Diplomate A.C.V.D., and
Dr. Sandra R. Merchant, DVM, Diplomate A.C.V.D.