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 difficulty breathing. In some people, a food allergy can cause severe symptoms or even a life-threatening reaction known as anaphylaxis. Food allergy affects an estimated 8% of children and up to 11% of adults. While there’s no cure, some children outgrow their food allergies. 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.