Allergy Skin Tests and Blood RAST tests are two ways to detect allergies in patients with Asthma, Allergies, Sinus Problems and Food Allergies. Skin Tests are more sensitive, reliable and clinically relevant than RAST. If skin tests cannot be done for some reason, RAST is the second alternative method. For Drug Allergies (Penicillin, Local Anesthetics such as Lidocaine and Xylocaine etc.) skin test is the only reliable method available. RAST for drug allergies is done but its value has not been validated by any reliable studies.
Allergy Skin Tests by the Skin Prick method pick up are not very sensitive but they must be done to screen out the more serious allergies. Skin Prick tests are almost painless. For antigens that show up negative by Prick tests it is necessary to test with the more sensitive Intradermal Tests. These tests are somewhat uncomfortable or maybe even painful for patients with low pain tolerance. For patients who are concerned about pain, a local anesthetic cream pre-applied on the skin is used to avoid the pain.