Physician Information | Testing Options | Allergy in Your Practice

Like any disease, the diagnosis of allergy begins with the patient’s clinical history and symptoms. Allergy testing may then be used to identify the specific causes of the allergic reaction. There are three common testing methods.

Today’s technology permits the physician to diagnose allergy from a blood sample. The test quantitatively measures immunoglobulin E (IgE) — the antibody responsible for the allergic reaction — that is specific to the allergens being tested. Thus, a single blood sample can provide allergen-specific IgE test results to a variety of allergens with greater patient comfort. The blood test does not require you to discontinue your antihistamine or other allergy medication and eliminates the risk of a severe reaction during the testing process. Blood testing can be used to test for sensitivity to all categories of allergens ( e.g., dust, animal dander, etc.) and is the preferred method for testing for food and drug allergies.

Traditionally, a patient is tested for allergy by applying a small quantity of allergen to a puncture in the skin and measuring the size of the reaction that develops. Skin testing is qualitative and highly technique-dependent, not to mention uncomfortable for the patient. Skin tests may be performed by either the skin-prick method or the intradermal method. In the skin-prick method, each allergen is applied to the skin as it is pricked with a needle-like device, while each allergen is injected into the deeper layers of the skin in the intradermal method. With both types of testing, the size of a reaction on the skin is monitored (the “wheal” and “flare”). While skin tests are very sensitive, they are not very specific, which means that a patient may not be allergic even if the test result is positive.

The provocation or challenge test is often used to assess food allergies. In this test, the patient ingests samples of various foods in capsule form and he or she is monitored for any reaction. In the best-controlled tests, neither the patient nor the physician know which food is in each capsule. Capsules of non-reactive “placebo” may be tested as well; such studies are called double-blinded placebo-controlled food challenges. Provocation tests must only be performed in the presence of medical personnel who are trained to handle patients who have severe allergic reactions.