Treating atopy: Keep patients comfortable without causing harm

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

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.

Photo 1: Periocular erythema and alopecia in an atopic dog.

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.

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.

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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?

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.

Photo 2: Periocular lichenification consistent with chronic atopy.

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.

As opposed to a bacterial pyoderma, if you are finding Malassezia yeast on your patient, a weekly bath in Malaseb shampoo along with oral ketoconazole 2.5-5 mg/kg bid for two to four weeks may help with pruritus. Some atopics greatly improve by treating the yeast that is usually secondary, although primary yeast hypersensitivity exists in some patients.

Photo 3: Ear edge alopecia in an atopic patient-rule out scabies!

Once the pyoderma has been treated, ectoparasites have been treated or ruled out, and if the patient presents with seasonal symptoms (usually ruling out food allergy, which is non-seasonal), atopy is the remaining differential. In a nonseasonal atopic patient, the patient may be dust-mite allergic or food-storage mite allergic.

An elimination diet trial is undertaken to rule out food allergy that might also be nonseasonal before proceeding to skin or serum testing.

If you choose to perform serum ELISA testing, get comfortable with the company you are using. The results must match the times of the year the patient is affected. Don't be afraid to ask questions. Some of the serum tests are guilty of false positives from molds. Molds tend to be "stickier" when performing serum testing in the lab and thereby register as false positives. If false positives are included in the allergy serum, there is a chance of sensitizing the patient to something it isn't already allergic to as well as taking up space for allergens that need to be included in the solution. Ask your lab about combining molds with outdoor pollens in the same solution. Data from human allergists suggests that molds produce protease enzymes that destroy outdoor pollens when placed in the same solution. Some allergy companies start their solutions at 200 pnu that in some patients, on the first dose, incites pruritus. If the patient is more pruritic after the injection, then the dose is too high! The desirable effect is less pruritus after the injection and increasing pruritus as you approach the next injection.

Photo 4: Acral lick granulomas in an atopic Doberman.

We administer our immunotherapy at weekly intervals for several reasons; foremost on the list, it helps with client compliance. Once the patient is under control, we will then extend the period between injections. There is such a thing as "rush hyposensitization" which consists of admitting the patient to the hospital and administering injections every three to four hours. Every region of the United States may differ as to what's pollinating when, and most local weather channels announce pollen counts daily. Get familiar with these because it will help you in choosing allergens for inclusion in the solution. In the Midwest, trees pollinate in the spring, grasses in summer and weeds in fall. House dust mites tend to be all year-round with some dust mite allergic patients flaring in spring and fall due to increased humidity, and others are only affected in the winter.

Most clients don't realize that dust mites are found in bedding, carpet, upholstery and mattresses — not in the furnace ducts.

Dust mites prefer darkness, increased humidity and increased temperature — the perfect combination of an exhaling, sleeping body (animal or human). Some people feel that if they frequently launder their bedding, this will reduce dust mite numbers. Most of us have our hot water tanks set at 125-degrees, but it takes 135-degrees or higher to kill dust mites.

I am often asked which I prefer, skin testing or serum testing for atopy. It is a loaded question because living in the Midwest with specific pollen seasons, some patients will not test positive using either method if tested during their "off" season. I feel that in a seasonally affected dog, the fall is the best time of year to test because they have been exposed to spring, summer and fall pollens. Skin testing is my first preference, but there are some atopic patients that just don't skin test positive and some that will not blood test positive. What is really frustrating is that some patients that you know are atopic will not test positive on the first or second skin or blood test — that of course is assuming the patient has been free of steroids and antihistamines. Another difficulty is starting immunotherapy during the time of year the patient is affected. It may be wiser to wait until the allergy season is over, or you might have a difficult time monitoring the response to the weekly injections.

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I have not discussed antihistamines or fatty acids, which in some patients, albeit very few, may be successful in reducing symptoms of atopy. Bathing on a regular basis is also helpful. It serves to mechanically remove the pollen that adheres to the coat and helps prevent accompanying bacterial pyoderma. Antibiotics or anti-yeast medications are usually an adjunct therapy to immunotherapy because most atopics acquire bacterial pyodermas, yeast dermatitis and flea allergy more so than nonallergic individuals. Short-term, short-acting steroids, such as prednisone or the antihistamine/steroid combination of Temaril P, may be helpful in atopics with a very short allergy season. Care must be taken to not inspire a bacterial pyoderma with steroid use and to be sure the owner discontinues the steroid once the season is over.

Immunotherapy can be successful 75 percent of the time. However, you need to be careful to choose an atopic patient, get familiar with the lab you're using, and pay close attention to match the time of year the patient is affected with what the allergy test results are telling you. Carefully monitor the immunotherapy process making sure the owner understands you are trying to achieve the correct dose of the correct concentration that alleviates the pruritus. Many owners feel they must get to the strongest vial of allergy solution, yet some patients are well-controlled on the initial low concentration. Remember, each allergic patient is an individual with his or her own prescription for immunotherapy. What that immunotherapy contains and in what concentration and dose is up to us to decide, and making that decision makes all the difference between success and failure of the program.

Dr. Jeromin is a pharmacist and veterinary dermatologist in private practice in Cleveland, Ohio. She is a 1989 graduate of The Ohio State University College of Veterinary Medicine and an adjunct professor at Case Western Reserve University's College of Medicine in Cleveland.