Although people often use the words interchangeably, a food allergy and a food intolerance are different. In a true food allergy the immune system reacts to a food protein, often within minutes, producing symptoms such as hives, swelling of the lips or face, itching, vomiting, and in severe cases anaphylaxis affecting breathing and blood pressure. Even tiny amounts can trigger a reaction.
A food intolerance does not involve the immune system in the same way and is generally caused by difficulty digesting a food, for example lactose intolerance from a shortage of the enzyme that breaks down milk sugar. Symptoms tend to come on more slowly and centre on the gut, including bloating, wind, cramps, and diarrhoea. Intolerances are uncomfortable but not dangerous, and the amount eaten usually affects how bad symptoms are.
Because the management is very different, it helps to get the right diagnosis rather than guessing. A doctor can arrange allergy testing for suspected allergies and may suggest a supervised elimination approach for intolerances. Avoid self-diagnosing through unvalidated commercial tests, and speak to a doctor or dietitian before removing major food groups.