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Blood Testing for Allergies

Blood tests for allergies are sometimes performed to find out what triggers an allergic reaction and are often used if a patient has a skin condition or is taking medications, such as antihistamines. Such medications can interfere with an allergy skin test, which is a common test used to identify allergy triggers, but in general do not interfere with allergy blood tests. However, there are disadvantages to each test which should be discussed with your health care provider.

The radioallergosorbent test (RAST), and the enzyme-linked immunosorbent assay (ELISA) test are two types of blood analyses most commonly used to diagnose allergies by looking at specific antibodies to allergens. In both, a small amount of blood is taken from the allergy sufferer and analyzed for IgE antibodies (allergic antibodies) to specific antigens. High levels of these antibodies in the blood indicate an allergic reaction.

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These blood tests may not be as sensitive as skin testing and tend to be more expensive, but can be useful in some situations. 

WebMD Medical Reference

Reviewed by Luqman Seidu, MD on May 09, 2012

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