Food Allergies in Dogs: A Diagnostic and Therapeutic Challenge

Categories: Dog Health Care
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Charles Hurty, DVM

Grove Veterinary Clinic

Bewport, Oregon

Food Allergies in Dogs: A Diagnostic and Therapeutic Challenge

Canine allergies typically fall into three general categories: flea allergy, environmental allergies (atopy), and food allergies.  In general, allergies in dogs can be a diagnostic and therapeutic challenge to owners and veterinarians.  Food allergies, in particular, are an extremely frustrating and irritating health problem for dogs and their people.

It is estimated that food allergies account for 10 to 15 percent of all allergic conditions in dogs.  A food allergy is defined as an adverse reaction by the immune system to ingredients in the food.  Typical clinical signs include itchy, irritated skin and/or intestinal or stomach upset.  Food allergies can happen at any age, though it is more common to recognize food allergies in dogs that are greater than 1 year of age.  We very often see food allergies in dogs that have been fed the same diet for years without many problems; these dogs develop a hypersensitivity to their diet over time.   Alternatively, some dogs quickly develop an allergy to many different types of food ingredients.  There are certain breeds in my experience that seem to be genetically predisposed to food allergies; these breeds include Golden Retrievers, Labrador Retrievers, Cocker Spaniels, Chow Chows, Dalmations, Boxers, English Bulldogs, French Bulldogs, West Highland Terriers, Pugs, and Boston Terriers.

The typical dermatologic clinic signs include recurrent ear infections, itchiness over the body, licking of the feet, and itchy rear ends.  The typical intestinal signs can include flatulence or gassiness, diarrhea, and vomiting.  Dogs may be troubled by only skin disease, only the intestinal signs, or have a combination of intestinal and skin clinical signs.   These clinical signs are typically non-seasonal (i.e. they occur year round and are not happening during a particular season.  Clinical signs that are associated with a particular season may be caused by an environmental allergen, such as pollen).

There is only one way to accurately diagnose food allergies in dogs and that is by performing an elimination diet trial followed by a dietary challenge.  There are some blood tests available, but the diagnostic usefulness and validity of the blood tests are questionable at best.  In order to perform a diet trial, we take a dog off of all the foods that he is currently consuming and put him on a diet that contains novel proteins and carbohydrates.  These novel proteins and carbohydrates are ingredients that the dog has never had before.  For example, this diet may contain some fairly exotic proteins, such as rabbit or kangaroo, and some atypical carbohydrates, such as sweet potato.  Another option is to feed one of the hydrolyzed protein diets, such as Royal Canin’s HP diet.  The selected food is fed exclusively to the dog for a minimum of 8 to 12 weeks.  If the dog’s clinical signs improve, a dietary challenge is the next step in diagnosing the food allergy.  We re-introduce the previous diets that the patient was fed and monitor for a return of clinical signs; if clinical signs (itchiness or intestinal problems) return, then the dog has a food allergy.  Several different diets may be tried in this manner before a response is noted.

As you can see, figuring out food allergies in dogs requires an extended period of time and can be quite challenging and frustrating.  This is definitely a problem that we are seeing on the rise in our clinic.  I feel that the genetic component of the disease plays a large role in the increase numbers of good allergy dogs.  If you are selecting a dog from a breeder, inquire about food allergies in dogs related to the puppy you are thinking about.  Food allergies should be considered in any dog with a prolonged history of non-seasonal, dermatologic or intestinal clinical signs.