The cause of food allergies is unknown. In some cases, allergies experienced during childhood may resolve in adulthood. Symptoms of a reaction can include digestive problems, hives or swollen airways. Severe reactions can be life-threatening. Antihistamine drugs treat mild reactions. A severe reaction needs an injection of the drug epinephrine and emergency room care Food allergy is an immune system reaction that occurs soon after eating a certain food. Even a tiny amount of the allergy-causing food can trigger signs and symptoms such as digestive problems, hives or swollen airways. In some people, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis. Food allergy affects an estimated 6 to 8 percent of children under age 3 and up to 3 percent of adults. While there's no cure, some children outgrow their food allergy as they get older. It's easy to confuse a food allergy with a much more common reaction known as food intolerance. While bothersome, food intolerance is a less serious condition that does not involve the immune system.