Screening for allergies is necessary in order to identify the specific allergens that trigger reactions. By identifying the specific allergens, an allergy sufferer can avoid them as much as possible to reduce the frequency of reactions.
There are several different tests available to identify allergens. Blood tests, which screen for antibodies produced in response to allergens, are commonly used. The most common blood test is the enzyme-linked immunosorbent assay (ELISA), which measures the amount of immunoglobulin E in the blood. Although blood tests can find a wide range of allergies, including those that may not even produce symptoms, they are less sensitive than other tests.
Skin tests are a very effective tool in screening for allergies. In skin tests, a tiny drop of a solution that contains the possible allergen is placed on the skin, which is then scratched or pricked so that the allergen enters the body. The skin is then checked for an abnormal reaction. In this way, specific triggers of allergic response may be identified. Depending on the situation, more extensive testing may be required to determine specific triggers. Allergy skin tests are commonly administered to diagnose conditions such as allergic rhinitis (hay fever) and eczema, as well as allergies to foods, bee venom, latex or penicillin.
In some cases, patients may be required to stop taking antihistamines or other medications before undergoing testing. In other cases, particularly those in which patients have had prior severe allergic responses, they may be required to take antihistamines before testing begins.