Food intolerances and allergies occur when your pets immune system reacts to something frequently innocuous the gastro intestinal tract and skin are two very sensitive organs which are exposed to all manner of things and sometimes the body cant cope when this happens your pets immune system reacts with food intolerance or allergies your dog will present with increased itchy skin or diarrhoea because it is reacting to a specific ingredient in its food such as animal or vegetable protein wh