Clinician’s Choice: Can You Resolve This Dog’s Chronic Dermatitis?

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Dermatitis is a common presenting complaint in canine patients, with dermatologic conditions typically accounting for 17% of patients seen in small animal general practice.¹ Diagnosing and treating dermatologic disease can occupy a significant portion of the general practitioner’s time, so it is worthwhile to follow a carefully considered approach to these cases.

There are 3 common causes of canine allergic dermatitis. Perhaps the easiest of these conditions to rule out is flea allergy. This is a relatively common condition in areas where fleas are regularly found, and it may coexist with other forms of allergic skin disease. If a patient’s allergies are not caused by fleas, there are 2 remaining differentials: food allergies and atopic dermatitis. The exact prevalence of food allergies is unknown, with estimates ranging from 1% of all pets to 15% of pets with skin disease.² The diagnosis of food allergies is often complicated by the fact that food allergies may be found concurrently with other allergic diseases.² Atopy is a more common cause of canine allergic dermatitis, with an estimated prevalence of 10% to 15% in dogs,³ but it is a diagnosis of exclusion. Seasonal signs may suggest atopy, but flea and food allergies must first be ruled out before diagnosing a dog with atopic dermatitis.

When a patient is presented for suspected allergic dermatitis, a standardized approach is recommended. First, any underlying medical conditions such as Cushing’s or hypothyroidism should be ruled out, followed by ruling out flea allergy with appropriate, consistent flea prevention. If a patient’s dermatitis persists despite flea prevention, food allergy should be ruled out with a food elimination trial. Finally, if there is no response to flea prevention or food trial, the patient can be diagnosed with atopy.