Has your doctor recommended you undergo allergy blood testing to determine what's causing your allergy symptoms? Allergy blood testing, or the Allergen-specific IgE antibody test (also referred to as Radioallergosorbent test or RAST) is one of several popular methods used today to diagnose specific allergies. It can also be used to monitor your progress during immunotherapy.

A Helpful Diagnostic Tool

While skin prick tests are often the first line of approach, many allergists use to test allergies, allergy blood testing can be used in conjunction with prick tests in order to provide a clearer picture of your body's allergic response. It can also be a valuable alternative when skin testing isn't an option.

Since prick tests rely on exposing your skin to tiny doses of suspected allergens, highly sensitive patients can be at risk for having a serious reaction from this method. Allergy blood testing simply requires a technician to draw some blood that can be used to test for reactions outside of your body. This makes it a safe and efficient alternative, although allergy blood testing can be more expensive than other allergy testing methods and can also take several weeks to get the results.

Interpreting the Results

If your blood allergy test results are positive to a certain trigger or multiple triggers, this information tells you what you'll need to avoid in the future. Just keep in mind that it's possible to show a blood response to a trigger without ever experiencing real symptoms.

There can also be a small number of people who have a negative response to something on their blood allergy test, yet they go on to have an allergic reaction later. This means that you can't rely on negative blood allergy testing results alone and should still proceed with caution if you suspect something could make you sick.

One Part of the Overall Picture

When your allergy blood testing results are inconclusive or your doctor needs additional information, he may also run a few other blood tests, including a complete blood count and a white blood cell differential. The results of these can provide additional clues of an allergic response.

Remember that allergy blood testing is one of several important measurements that your doctor can use as part of a broader strategy to diagnose and treat your allergies, but the results need to be interpreted as part of your broader health history.


American Association for Clinical Chemistry (AACC)/Lab Tests Online


American College of Allergy, Asthma and Immunology


U.S. National Library of Medicine/Medline Plus