An intradermal allergy test involves injecting a small amount of allergen under the skin. This is typically done after a scratch test if that scratch test has proven inconclusive. Intradermal allergy tests can test a for a variety of allergies including insect sting allergies. 

Using a very thin needle, the allergist injects a diluted form of the allergen just below the skin. The section of skin is then closely observed for at least 15 minutes. If the skin reacts to the injection and develops a red, itchy wheal, this indicates that the body has responded to the allergen with an allergy antibody, confirming an allergy. Generally speaking, the larger the reaction in the skin, the higher the patient’s sensitivity to the allergen is.

Allergy skin tests in general are very reliable techniques for diagnosing allergies. While not 100 percent accurate, intradermal allergy tests are still widely considered one of the most accurate methods for diagnosing allergies.

You can have a false positive with an intradermal allergy test, or you may react to a substance during testing, but not in the regular course of your life.