Tests to Diagnose Seasonal Allergies

To determine 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 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.

Skin prick reactions 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.

Intradermal tests are 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 IgE antibodies in your blood. If the antibodies are present, it indicates a true allergic reaction. RAST is the safest type of allergy test, but compared with a skin prick test, it's less likely to pick up sensitivity to a substance, it takes longer to produce results, and it can't test for as many allergens at once.

This 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.