If you haven't had an allergic reaction for a long time, your doctor may want to perform a food challenge to determine whether you've outgrown your food allergy. A food challenge consists of trying (under the careful supervision of a qualified doctor) a small amount of the food that has caused reactions in the past.
Caution: Never attempt a food challenge on your own. Food challenges should be performed under the close supervision of a qualified allergist who has emergency medications and equipment on hand to treat a severe reaction should one occur.
To reduce the risk of a reaction, your doctor should first perform a blood test to measure the level of antibodies to the food that has triggered reactions in the past. The lower the level of antibodies to the specific food, the less likely you are to react when you actually consume the food.
Back in July of 2004, my colleagues and I did a study published in The Journal of Allergy and Clinical Immunology, in which we provided guidelines for using food-specific antibody levels to determine conditions in which we would feel more comfortable recommending a food challenge. We generally recommend a challenge when the patient has a 50-50 chance or better of passing.
If you haven't experienced a reaction for some time, consult with your allergist to determine your chances of having outgrown the allergy and to see if additional testing may be able to prove it. But remember, don't try a food challenge on your own!