Asthma and Allergy > Allergies > Tests

Tests for allergies

The first step in treating allergies is to determine which substances are causing the allergic reaction. Several different tests can be used.

Skin test

Skin testing is the most common method used to test for allergies. In this test, a small amount of the suspected allergen is placed on the skin. The skin is then pricked or scratched so that the allergen gets under the skin’s surface. If the skin reddens and swells, forming a hive, the test is considered positive. It usually takes 15 minutes to 20 minutes to get results.

Skin testing is mildly uncomfortable. Patients tend to rate the discomfort as a one or two out of 10. The ease and immediate results make skin tests the preferred method to test for allergies.

RAST test

The RAST (radioallergosorbent) test is a blood test that measures the levels of allergy antibody (IgE) in your blood when it is mixed with a series of allergens. This test usually is only done on people who cannot have skin testing, such as people who have skin conditions or are on certain medications.