Food allergy is an uncommon problem in dogs and it can start at any age. A change in diet is not necessary for development of food allergy. About 70 percent of affected pets develop allergies to food ingredients that they have been fed for a long time, usually more than two years. In fact, if your dog has an immediate adverse reaction to a new food, it is probably not an allergic reaction, because it takes more than one exposure to produce an allergic reaction.

Food ingredients most commonly responsible for allergies are beef, chicken, fish, eggs and milk. The tendency to develop allergies is genetically determined. Dogs with other allergies like inhalant allergies or atopy may be at increased risk for developing a food allergy.

The clinical symptoms of food allergy resemble those of other types of allergies. These two disorders may have the same clinical symptoms and the same distribution of itchiness or pruritus over the dog's body. In some cases, it is impossible to differentiate between inhalant allergy and food allergy by clinical appearance alone.

Food allergy should be ruled out first because it is the easier of the two disorders to control by eliminating the offending food ingredient from the dog's diet. Food allergy is ruled out by feeding a diet consisting solely of food ingredients to which the animal has not been previously exposed – an elimination food trial. This trial should be performed before considering expensive tests for other types of allergies.

What to Watch For

Itchy (pruritic) skin, especially around the face, paws and ears

Bad skin odor

Excessive scaling

Red bumps or papules

Ear infections

Self-inflicted skin trauma resulting from severe itching

Diarrhea and vomiting, although most dogs with food allergy only develop skin problems