An allergy is the response of the immune system to substances that are usually harmless, such as foods, pollens, medicines, molds, pet hairs and house dust mite. When a person comes in contact with a particular allergen to which they are allergic, an allergic response is triggered causing symptoms which include sneezing, wheezing, rash, itchy eyes and sickness. Rates of allergy are increasing throughout the world and may affect up to 30-35% of people at some time in their lives.