Food Allergy Tests:  Blood and Skin Tests

There are a variety of food allergy tests to choose from when determining whether or not your child has food allergies.

Allergy skin tests and allergy blood tests are the 2 categories of testing. Skin testing is the most reliable form of allergy test, however if your child is unable to tolerate skin testing, an allergy blood test may be indicated.

If your suspect your child may have food allergies, it is very important to get them to take food allergy tests to determine what and how severe the allergy is.

Food Allergy Skin Tests

There are 2 main tests for food allergy, skin prick tests and intradermal tests.

A skin prick test is performed by placing a small amount of possible allergen on or underneath the skin to see if there is a reaction. If a red, itchy, swollen area on the skin develops (called a wheal), it is interpreted as positive and the individual is considered allergic to that food. A larger wheal indicates a more severe allergy than a smaller wheal.

Less common skin tests for allergies include the intradermal test. During this test a small amount of solution containing the allergen is injected in the skin. An intradermal test is usually performed after the skin prick test returns negative results however an allergy is still suspected. The intradermal test also causes many false positive results, which may cause someone to avoid a food he is not truly allergic to. This test is fairly rare.

Food Allergy Blood Tests

Food allergy blood tests look for antibodies. Although they are not as reliable as skin tests they are regularly used because they are easier to do and are less stressful on the patient. An allergy blood test is simply a blood draw and is usually a good option for children who cannot tolerate allergy skin tests.

The 2 major types of blood tests used to test for allergies are the ELISA and the RAST.

ELISA stands for enzyme-linked immunosorbent assay and measures the level of IgE antibodies in the blood. IgE levels are often higher than normal in people with allergies.

RAST stands for radioallergosorbent testing and detects IgE reactions to allergies in a test tube. RAST tests are considered when there is a fear of a severe reaction with a skin test or a child cannot tolerate the skin test.