CAP-RAST Testing

CAP-RAST is a type of blood test, which may be recommended by your allergist to check for allergies.

What is CAP-RAST Testing?

When you have a reaction to an allergen, your body identifies the substance as harmful and releases a protein called immunoglobulin E (IgE). A CAP-RAST is a blood test which determine if IgE attaches to the allergen. But unlike some other types of blood tests, the CAP-RAST can also measure the amount of IgE directed at the allergen, which helps your allergist determine if you are allergic to a specific food or other allergens.

This type of blood allergy testing is often used in food allergies. Although it can detect the levels of IgE and confirm you are allergic to a specific allergen, the test will not determine how severe a reaction you may have.


The procedure is relatively simple. It involves taking a small amount of blood and applying it to material containing the suspected allergen. A positive reaction to the allergen indicates an allergic reaction is likely. CAP-RAST testing may also be done in conjunction with skin allergy testing to confirm a diagnosis.

In some instances, a CAP-RAST may also be done if skin allergy testing may cause a systemic allergic reaction in highly sensitive patients. One advantage of CAP-RAST testing is medication does not need to be stopped prior to the test. After the test, you allergist will go over the results and explain what the result indicate.

For more information on CAP-RAST testing or other types of allergy tests, please call one of New York City’s top allergy doctors Dr. Boyan Hadjiev.

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