The best treatment is preemptive: Avoid the foods that cause you to have an allergic reaction. You have some help in this game plan—the Food Allergen Labeling and Consumer Protection Act, which took effect January 1, 2006, requires food manufacturers to disclose in plain language whether products contain any of the eight most common causes of food allergies.
At times, however, you may not be able to avoid exposure to a food or ingredient that triggers an allergy symptom. A tiny amount of peanuts or some plant oils might be on a restaurant's cooking utensils. For minor reactions, over-the-counter antihistamines can effectively alleviate symptoms.
For a serious, anaphylactic reaction, you may need to call an emergency medical response team or go to the hospital to have epinephrine administered. If you know you have a serious food allergy, and have had severe reactions in the past, you should be carrying an auto-injector to give yourself a dose of epinephrine (common brands include the Anapen, EpiPen, and Twinject).