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Blood Testing for Allergies


Types of Blood Testing

You may hear several different terms used to reference blood testing for allergies, including RAST, ELISA, and immunoassay testing. Generally speaking, these tests all achieve the same goal: identifying the presence of allergen-related antibodies in the blood.

Formerly called RAST testing, ELISA testing is now the gold standard for allergy blood testing. AllerVie Health performs allergen-specific IgE (Immunoglobulin E) testing, commonly known as ELISA/EIA testing, utilizing ImmunoCAP by ThermoFisher, when conducting allergy diagnostics.


The RAST test was the most common blood test until recently for diagnosing allergies. This test uses radioimmunoassay testing to identify specific antibodies in the blood. As a result, the diagnostician cna then confirm specific substances to which the patient is allergic. RAST testing has been replaced in recent years by the ELISA test.


The enzyme-linked immunosorbent assay test, known as the ELISA for short, identifies the exact amount of specific antibodies in the blood. This provides the detail needed to develop specific and customized plans in the treatment of allergies.

ImmunoCAP™ Tests

ImmunoCAP tests are a form of ELISA test. Since it can be difficult to differentiate between allergies and other respiratory ailments, ImmunoCAP testing gives diagnosticians a way to confirm or rule out the presence of allergies. ImmunoCAP tests can be used in the diagnosis of hundreds of allergens including weeds, mold, pollens, food, and animal dander.

How Can Blood Testing Diagnose Allergies?

Blood testing diagnoses allergies by identifying the presence of allergen-related antibodies in the blood. When the body’s immune system triggers an allergic reaction, it releases more Immunoglobulin E (IgE) into the bloodstream. Typically, the acceptable upper limit of IgE is between 150 and 300 UI/ml. When a blood test identifies IgE levels higher than this range, it can serve as confirmation of an allergic response.

What Types of Allergies Can RAST Test For?

RAST tests can be used to test for a range of allergies, including drug allergies, seasonal allergies, food allergies, and pet allergies. Determining which test is the best option should be done in consultation with your allergist and involves several different factors, including age, suspected allergy, and the severity of a patient’s reaction to an allergen.


Which Tests Are Better, Skin Or Blood?

You should work in consultation with your allergist to determine which test is the best option for you. In general, allergists prefer to avoid skin tests in younger patients. Skin tests are also riskier for those with eczema or other skin conditions.

Blood tests such as the ELIZA test can also provide the detail needed to develop a customized treatment plan. One advantage of skin tests, however, is that they produce fast results, while blood tests can take a few days to process. If you are interested in allergy testing, discuss all your options with your allergist.