The diagnosis of allergies, or allergic disease, is based on the clinical history, family history, physical examination, skin tests and laboratory tests. The tests serve to confirm the diagnosis of allergic disease and to identify potential allergic triggers, knowledge that is useful to guide allergen avoidance strategies.
When you see an allergy specialist, allergy tests will likely be performed to determine whether you are allergic and what you are allergic to. Skin prick tests are carried out by applying drops of allergens to your skin, usually on your back and occasionally on your arm, and then scratching or pricking though them. Skin tests are used to test for allergies to environmental allergens, such as pollens, molds, dust mites and animal dander, and also to foods. If you are allergic to an allergen, you will get a bump and redness where the skin is pricked. After a short time, each skin test reaction is measured for swelling and redness. A large enough skin reaction is a positive skin test. This means an allergy may exist to the allergen placed at that site. Your doctor will compare your skin prick test results with your history of symptoms.
Allergy blood tests evaluate for sensitizing IgE antibodies that bind to environmental and/or food allergens and may be performed if skin testing cannot be done, or to gain additional information.