What should you know about the most common food allergy?

A food allergy occurs when the immune system reacts to a food protein. Symptoms may include hives, swelling of the lips or face, vomiting, wheezing, or an itchy throat. A food reaction can be mild on one occasion and more serious on another, so do not test a suspected trigger at home.

Food intolerance is different: it usually involves difficulty processing a food rather than an immune reaction. A careful history helps distinguish allergy, intolerance, infection, and skin or digestive conditions. [Food Allergy](/conditions/food-allergy/) explains the condition in more detail.

Stop eating the suspected food and note the ingredients, amount, timing, and symptoms. Do not remove several food groups without clinical guidance, particularly for a child, because an unnecessarily restricted diet can affect nutrition. A clinician may recommend [Allergy Testing](/treatments/diagnostics-and-screening/allergy-testing/) based on the history rather than testing every food.

If an allergy is confirmed, learn how to read labels, avoid cross-contact, and follow the personalised emergency plan. Tell schools, carers, restaurants, and close contacts about the allergy and prescribed medicines.

Call emergency services immediately for trouble breathing, throat or tongue swelling, faintness, collapse, or symptoms affecting more than one body system after eating. These can indicate [Anaphylaxis](/conditions/anaphylaxis/). Use prescribed adrenaline exactly as instructed and follow emergency advice; [Anaphylaxis Emergency Treatment](/treatments/acute-and-urgent-care/anaphylaxis-emergency-treatment/) describes urgent care.

Ask whether the reaction pattern fits allergy, which tests are appropriate, how to maintain balanced nutrition, and what your written emergency plan should say. Ask when supervised challenge testing might be considered and where it must take place.