What do allergists do to determine what a patient is allergic to?

Allergy tests. Allergy tests can generally be performed two ways: skin testing and blood testing. Skin testing is done either via the "scratch" or "prick" testing method or via a small injections in skin (called an intradermal test). Blood allergy testing (called rast) testing can also be done. Both methods look for specific allergic antibody (called ige).