Responses of dogs with food allergies to single-ingredient dietary provocation

OBJECTIVE: To characterize specific food ingredients causing allergic reactions in dogs and to assess cross-reactivity between proteins derived from a single animal source or from different plant products. DESIGN: Prospective study. ANIMALS: 25 dogs with histories and cutaneous signs consistent with food-allergic dermatitis. PROCEDURE: Dogs were fed a food-elimination diet until resolution of clinical signs and then challenged with their original diet. A diagnosis of food allergy was made if there was complete return of pruritus within 14 days of challenge exposure. After diagnosis, dogs were fed the food-elimination diet until signs related to dietary challenge abated. The dogs then were fed beef, chicken, chicken eggs, cows' milk, wheat, soy, and corn in single-ingredient provocation trials for 1 week. Any cutaneous reactions to these food ingredients were recorded by their owners. RESULTS: Beef and soy most often caused adverse cutaneous reactions, although all ingredients induced clinical signs in at least 1 dog. Mean number of allergens per dog was 2.4, with 80% reacting to 1 or 2 proteins and 64% reacting to 2 or more of the proteins tested. A significant difference was found between dogs reacting to beef versus cows' milk and between dogs reacting to soy versus wheat; thus, the hypothesis of cross-reactivity to ingredients derived from a single animal source or to different plant products was not supported. Similar differences between chicken meat and eggs were not identified. CLINICAL IMPLICATIONS: Long-term management of dogs with food allergies is facilitated by identification of the most commonly encountered food allergens. Because cross-reactivity cannot be verified, each protein source should be included separately in food-provocation trials.