An allergy is the response of the body's immune system to normally harmless substances, such as pollens, foods, and house dust mite. Whilst in most people these substances (allergens) pose no problem, in allergic individuals their immune system identifies them as a’ threat’ and produces an inappropriate response. It is exaggerated because these foreign substances are usually seen by the body as harmless and no response occurs in nonallergic people. In allergic individuals, the body recognizes the foreign substance and one arm of the immune system generates a response. Allergies are classified into IgE mediated and non-IgE mediated allergies. In IgE mediated allergies the immune system produces exaggerated amounts of a distinct class of antibodies known as IgE antibodies that are, specific for the particular offending allergens.