Treating atopy: Keep patients comfortable without causing harm

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Oct 01, 2005

In fighting allergies, our goal as veterinarians is to keep these patients comfortable without causing harm.


Photo 1: Periocular erythema and alopecia in an atopic dog.
In a dermatology referral practice, 30 percent or more of our patients are atopic whereas in the general population the estimates range from 3-15 percent of all patients seen are atopic. Some days at the office, I would beg to differ that these percentages are higher! Anecdotally, I think all of us would agree that we are seeing more allergy than ever before. In human allergists, the incidence of allergy in children has increased due to dietary changes, including lack of fish in the diet and a reduced intake of fatty acids. Hopefully, the following suggestions will help you get your canine patients through a more comfortable allergy season.

The first consideration in successfully treating an atopic patient is to know how to recognize atopy. It sounds simple, but there are many diseases masquerading as atopy. Atopy can start anywhere from 3 months to 3 years of age. It is likely repetitive, e.g. occurs at the same time every year. If you have a 12-year-old dog that you feel has "become" atopic, think again and go through the differentials to rule in atopy. Atopy likes to involve the face, feet and rectal area. The patient likes to rub his face, lick his feet and sometimes scoot. Besides being inhaled, we now know that percutaneous absorption of the allergen is important in canine atopy and what better place to absorb the allergen than the non-haired areas of the body, such as ventral feet and rectal area. Other manifestations of atopy include recurrent otitis, recurrent yeast or bacterial pyoderma including acral lick granulomas, ocular discharge, recurrent urinary tract infections, recurrent demodicosis, cutaneous histiocytosis and upper respiratory symptoms. Specific atopic breed idiosyncracies include German Shepherds, Labrador Retrievers and Boxers presenting with crusty, alopecic ear edges as seen in canine scabies, Siberian Huskies presenting with periocular and perioral crusting usually seen with zinc responsive dermatosis and various breeds presenting with cutaneous histiocytosis that responds to therapy for atopy, i.e. immunotherapy.


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Before declaring a patient atopic, one must rule out the differentials for atopy that include ectoparasitic infections (scabies, flea allergy, Cheyletiella), bacterial pyoderma, food allergy, Malassezia yeast dermatitis and dermatophytosis. When seeing a suspected atopic patient for the first time, we check skin scrapings for scabies/demodex mites, combings for Cheyletiella mites/fleas, ear smears for yeast or bacteria and skin smears and nail bed smears for yeast or bacteria.

If a bacterial pyoderma is present and has not been treated or if yeast is found on skin smears, we will start by treating the pyoderma or yeast dermatitis first until total clearing plus one week. At that point, the owner is to call with a report as we need to know if despite clearing the lesions, the patient is still pruritic. If the patient is not pruritic but presents with a recurrent pyoderma, how long does it take to resolve the pyoderma, and more importantly, how soon does it recur?


Photo 2: Periocular lichenification consistent with chronic atopy.
The bacterial pyoderma should be treated with a minimum of four weeks of antibiotics along with antibacterial bathing and no steroids. In some patients, even a small dose of steroid is enough to immunosuppress the skin's immune system and not allow resolution of the pyoderma. Probably one of the most common mistakes we see is bacterial pyoderma treated with antibiotics and steroids.

These patients never seem to crawl out of their dermatologic problem because initially the steroid takes away the inflammation associated with the bacterial infection but goes on to immunosuppress the patient. So, at the end of the initial two to three weeks of antibiotics, the pyoderma is back even worse than before. The normal inclination is to repeat the steroid at a higher dose this time, and the same thing happens, but now the pyoderma is even worse than when you started.