Diagnostic Tests for Allergies

The most common tests for allergy are:

  • IgE (immunoglobulin E) skin tests. These are the most common allergy tests. Skin tests for allergies measure IgE antibodies to specific allergens. A small amount of allergen is applied to the skin. The area is pricked or scratched. If a person is allergic to the allergen, a reaction occurs. A small raised bump that looks like a mosquito bite appears. Testing for many allergens may be done at the same time. An allergist may also test intradermally. A small amount of allergen is injected just under the skin. This type of skin testing is more sensitive than prick or scratch testing.

  • Blood tests. Blood tests for allergies also measure IgE antibodies to specific allergens in the blood. The testing that is most commonly used is called RAST (radioallergosorbent test). Blood tests may be used when skin tests can't be done. For example, in a person with a skin condition. A positive blood test does not always mean have a specific allergy. These tests usually cost more than other allergy tests.

  • Challenge test. This test is always supervised by an allergist. A person eats or inhales a very small amount of an allergen and is closely monitored for an allergic reaction. Challenge testing is usually done to test for food or drug allergies.