A food allergy is a reaction to food by the body’s immune system. Food allergy is different from food intolerance which doesn’t involve the immune system. In most situations, protein in the food causes the immune reaction. Often, the protein sources come from animals—meat, eggs or dairy products. Occasionally, a carbohydrate source can also be involved. Common foods that induce allergies include beef, chicken, fish, dairy products, wheat gluten, corn and soy protein. Dogs and cats can be allergic to more than one food ingredient in the diet.

Clinical signs of a food allergy include itchiness, licking and chewing of the paws, flank, groin, neck and ears. Cats often scratch their faces and ears. The itching occurs during all seasons. Some dogs may have recurrent ear inflammation or infections. Gastrointestinal signs such as chronic vomiting, diarrhea and frequent bowel movements may also occur. It is common for both skin signs and gastrointestinal problems to be present and these problems tend to persist or recur.

No single specific test exists that can diagnose a food allergy. Although allergen blood testing is available, these tests are not very accurate. It is important to provide your veterinarian with a thorough and complete history of all foods and treats your dog or cat eats, including table scraps, chew toys and medications that are chewable or contain flavorings.

A dietary food trial may be used to diagnose a food allergy. A food trial involves feeding and elimination diet for two to four months. Ask your veterinarian what diets he or she recommends. There are homemade diets, hydrolyzed diets and commercial diets that are made specifically for food allergies. During the food trial, no other foods or treats can be fed. Your pet must be watched closely to make sure it does not get into the garbage, eat things outside or obtain food from children, neighbors or friends. Depending on the severity of the clinical signs, medications may to decrease itching and inflammation. Eventually many medications can be discontinued.

Prognosis for treating a food allergy is good as long as the dog or cat is not re-exposed to the ingredients that trigger the immune response.

Dr. Karsten Fostvedt is a veterinarian at St. Francis Pet Clinic in Ketchum.

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