Determining food intolerance

Food intolerance is a problem digesting or responding to a food component; it differs from an immediate food allergy, which can involve hives, swelling or breathing problems. Symptoms may include bloating, abdominal pain, wind, nausea or diarrhoea, and they can have many causes. The food may not be the only explanation.

A clinician will ask when symptoms begin, how long they last, the portion eaten, bowel changes, weight change, medicines and family history. Testing depends on the suspected food. There is no universal blood test that can confirm every intolerance, and commercial sensitivity panels may encourage unnecessary restrictions.

Keep a diary for several weeks with foods, portions, symptoms, bowel movements and other relevant factors such as stress or antibiotics. Avoid removing many foods at once. If a clinician recommends elimination, follow a defined plan and reintroduce one food at a time so the result is interpretable.

Seek nutritional guidance if you need to exclude dairy, gluten or several staple foods, particularly for a child, during pregnancy, or if you are losing weight. Do not start a gluten-free diet before assessment for coeliac disease unless your clinician advises it, because changing gluten intake can affect testing. Read more about [Food Intolerance Testing](/treatments/diagnostics-and-screening/food-intolerance-testing/) and [Nutrition Counselling](/treatments/lifestyle-and-wellness/nutrition-counselling/).

Arrange a medical review for persistent diarrhoea, blood in stool, repeated vomiting, unexplained weight loss, fever, night-time symptoms or symptoms that wake you. Get emergency help for throat or tongue swelling, wheezing, breathing difficulty, faintness or a rapidly spreading itchy rash after food, because these may signal an allergic reaction rather than an intolerance.

Ask which diagnoses should be considered, whether you need blood or breath testing, how long an elimination trial should last, and how to reintroduce the food. Discuss replacement foods so your diet still supplies enough energy, protein, calcium and fibre.