Allergies can be characterized by hyper responsive reactions towards certain components (allergens). In cats and dogs, the major clinical signs are dermatological problems and gastro-intestinal signs. Occasionally, other symptoms like asthma or rarely arthritis may be related to an allergic reaction as well. In the paragraphs below, allergic dermatitis and gastrointestinal problems related to allergies are described separately. However, individual allergic pets can show both types of symptoms simultaneously.