A small number of foods account for the majority of allergic reactions. In children, cow's milk, egg, peanut, tree nuts, soya, and wheat are the most frequent. In adults, peanut, tree nuts, fish, shellfish, and sesame are common, and many adult allergies, particularly to nuts and seafood, persist for life. Sesame has been increasingly recognised and is now a labelled allergen in many regions.
Reactions occur when the immune system mistakenly treats a food protein as a threat. Symptoms can appear within minutes and include an itchy mouth, hives, swelling of the lips or face, tummy pain, vomiting, and in severe cases breathing difficulty and collapse (anaphylaxis). The amount of food needed to trigger a reaction varies, and someone can react to traces.
Food allergy is different from food intolerance, which involves digestion rather than the immune system and is not life-threatening. If you suspect a food allergy, see a doctor before cutting out major foods, especially in children, because unnecessary restriction can affect nutrition. A doctor can arrange allergy testing and, where needed, a referral to an allergy specialist.