Q: How do allergy skin tests work?
A: There are two types of skin tests. During the first type of skin test, called a prick test, a drop of a suspected allergen is pricked on the surface of the skin. The test is performed on the back or forearm. Many suspected allergens can be tested at the same time.
Sometimes only a small number of selected allergens is necessary. If you have redness and swelling at the test spot, then you might be allergic to this allergen. The allergist will help to interpret this result.
Sometimes the doctor will recommend a second type of test called an intradermal test. In this type, a small amount of the suspected allergen is injected into the skin of the forearm.
Skin testing is fast. For both types of skin tests, positive reactions appear within 20 minutes.