In dogs, common clinical signs of food allergy are related to the skin and include itching, scratching, biting and/or chewing of some or all of the following areas: ears, around the eyes and muzzle, paws, underarms, groin, and anus. In some cases, there may also be episodes of vomiting and/or loose stools, excess flatulence, and stretching (posture of relief). Food allergy must be distinguished from dietary intolerance, which does not affect the skin but manifests itself primarily with vomiting and diarrhea.
To determine if your dog has food allergies, ask your veterinarian to place your dog on an elimination test diet. This remains the most reliable and accurate method of diagnosing food allergies. Once a diagnosis of food allergy has been made, your dog can then be put on a commercially available "'hypoallergenic" diet that avoids those foods to which your dog is allergic.
If, on the other hand, your dog proves not to have a food allergy, there are many other possible reasons for itching and scratching in dogs. Your veterinarian can do other tests to try to determine a cause.