A Answers (2)
Anita Gupta, Anesthesiology, answeredTo pinpoint allergies, allergy skin tests (also called prick tests) are used. The skin is pricked with an extract of a specific allergen, and then the skin’s reaction is observed. Redness and irritation can be seen within 15-20 minutes. Another test is serum-specific IgE antibody testing. It is a blood test that looks at various components of the immune system. The immunoglobulins may be abnormal if an allergy is suspected. Eosinophils, a cellular component of the immune system, can also be tested. An elevated level of these cells is usually associated with an allergic reaction. Diagnosis of specific allergies is important so one can lessen or prevent further allergic reactions.
RealAge answeredTo diagnose your seasonal allergies, including whether -- and which -- allergens may be causing your symptoms, your doctor may order one or more of the following tests:
- Skin Prick or Puncture Test -- A skin prick test is a simple allergy testing procedure in which a number of allergens (in droplets) are placed on the skin -- usually on the forearm, upper arm, or back. The skin is then gently pricked, which allows the allergens to get into the skin cells. If this produces an allergic response -- temporary redness, swelling and itching at the test spot -- it means you're sensitive to that allergen. And the greater the reaction, the more likely it is that you're not only sensitive to it but also allergic to it. Reactions to skin prick allergy tests usually appear fairly quickly, within 15-20 minutes. But it's also possible to have a delayed reaction several hours later. If this happens, notify your doctor or nurse.
- Intradermal Test -- This test is similar to a skin prick test, but the allergens are injected under the skin using a syringe and a much more dilute solution. The intradermal allergy testing procedure is typically used when results from skin prick tests are unclear or if repeated tests have not triggered a reaction to any allergens.
- Antibody Blood Test (RAST) -- A RAST (radioallergosorbent) blood test looks for specific immunoglobulin E (IgE) antibodies in your blood. If the antibodies are present, it most likely indicates a true allergic reaction. RAST is the safest type of allergy test, but compared with a skin prick test, it takes longer to produce results and it can't test for as many allergens at once.
This type of allergy test is typically used only in special circumstances where skin testing is not advised -- for example, if a person has a severe skin condition or is taking certain medications. Ask your doctor about the risks versus the benefits of both the skin prick test and the RAST blood test.