Food allergies are caused by a specific, reproducible immune response to a particular structural aspect of a "problem food." Food allergies most commonly are caused by allergic antibodies (IgE) to the food(s) in question, or more rarely may result from other specialized immune pathways (non-IgE mediated). Once the allergy is identified, avoidance of the specific problem food will resolve the symptoms. Most allergic reactions to foods result from unintentional exposures in individuals with a known food allergy.
Nine problem foods are responsible for 90 percent of all IgE-mediated food allergies:
Most young children with an IgE-mediated food allergy will outgrow the allergy by adolescence; however only 20 percent of children allergic to peanuts will outgrow the allergy.
These "classic food allergies" usually have an almost immediate onset of symptoms that are related to anaphylaxis. In general, allergic symptoms can occur within two hours of eating the problem food. Typically, reactions start within minutes. Most people experience skin irritation, particularly itchy rashes with hives or facial swelling. Like anaphylaxis, signs include rash, rapid tissue swelling, vomiting, diarrhea, eye-nose-throat swelling, breathing problems, heart palpitations and/or fainting.