In order to properly diagnose your food allergy, your doctor may order either a skin-prick test, or a blood test. Both tests can determine your specific allergen.
Skin-prick tests are the primary means of diagnosing an allergy. In a skin-prick test, a tiny bit of each potentially problematic food is inserted under the skin. If the skin develops a bump or other noticeable change of appearance, you are allergic to that food. Results can usually be seen in 10 to 20 minutes
Depending on your personal medical history and the problem at hand, your doctor may order a blood test. A RAST test (short for “radioallergosorbent test”) can measure your immune system’s response to an allergen by detecting the amount of IgE antibodies made in response to suspected food proteins. In a RAST test, a sample of the patient’s blood is added to the suspected food protein, and then tested for the amount of IgE antibodies made in response.