In dogs, a food allergy or intolerance generally appears as gastrointestinal (GI) upset, leading to vomiting, diarrhea, excess gas or weight loss; or intense itching and scratching, which can involve the ears, face, feet, tail and stomach. Itching can result in red, irritated-looking skin.
Food allergy or intolerance can make both you and your dog miserable. So, it's important to see your veterinarian as soon as possible if your pet experiences any of these symptoms. He or she can work with you to choose a special dog food for your dog's allergies.