Allergen-Specific IgE Testing

Also known as: allergen-specific immunoglobulin E blood test, allergy blood test, ImmunoCAP, RAST, Skin prick testing, allergy skin test, allergy testing.

What is allergen-specific IgE testing?

Allergen-specific IgE testing can either be a skin test or a blood test. The skin test is the most common way of testing for allergies and is relatively painless. It works by directly challenging the allergy cells in your skin to a specific allergen.

The blood test checks to see if your body has made allergy antibodies (IgE antibodies) to the specific allergens. This is generally used if skin tests are unsafe to use or do not work, like if you are taking certain medications or have skin conditions that would interfere with the testing.

What happens during the procedure?

The skin test involves using a plastic device that introduces specific allergens like tree pollen, grass pollen, weed pollen, dust mite, cat, dog, mold, and/or foods into the top layer of the skin and allows your allergy cells in the skin to react to these. When there is a positive allergic reaction, it produces a localized itchy red bump. These are done in the allergist’s office and results take about 15 minutes.

The blood test is done at a lab where a technician uses a syringe to draw blood from the arm. Results can take several days.

Is any special preparation needed?

You need to be off all antihistamines for about one week before skin testing is done. Antihistamines can be prescription eye drops, prescription nasal sprays, or over the counter oral medications. If you have questions about which medications you can or cannot take prior to your visit, call your Allergist and they will help you. There is no special preparation needed for the blood test.

What are the risk factors?

Both skin and blood tests are very safe. In rare occurrences, a patient can have a systemic allergic reaction to the skin testing, which is why this needs to be done in a board certified Allergist’s office. With the blood test, some mild bruising may occur at the site on the arm where the blood is drawn.

Reviewed by: Amy S Feldman, MD

This page was last updated on: May 05, 2021 10:55 AM

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