An allergic reaction is an unwanted side effect caused by an inappropriate response of the immune system to various substances such as pollens, mold, dust or insect bites, certain foods, drugs and chemicals. Exposure to them triggers a reaction, usually through itching, sneezing, coughing, tearing, vomiting or diarrhea. The most frequently encountered allergies in Swissys are reaction to certain types of food, flea bites and pollen. Food allergies occuring at a young age sometimes disappear, i.e. the dog outgrows the allregic reaction eventually. Becaue the cause of an allergy is often difficult and sometimes impossible to determine, allergies can be very frustrating for the owner, and patience is often the only recourse.