IBS and food intolerance tests

Food intolerance describes difficulty handling a food or ingredient and is different from an immune-mediated food allergy. Lactose intolerance, for example, may be assessed with a breath test or by observing symptoms during a structured dietary trial. Other suspected triggers may need a planned elimination and reintroduction process. Symptoms such as bloating, abdominal pain, diarrhoea and constipation overlap with IBS, so a positive reaction to one food does not automatically explain every symptom. Coeliac disease needs medical testing before gluten is removed, because avoiding gluten can affect the results.

Write down meals, ingredients, timing, bowel movements and symptoms, including symptom-free days. Bring the record to a clinician or dietitian. Avoid buying multiple unvalidated intolerance tests or cutting out many foods at once. A professional may suggest one focused change, followed by reintroduction, while checking that your diet remains adequate. Keep drinking fluids, and seek help if diarrhoea or vomiting makes it difficult to stay hydrated. Use the results to build a practical eating pattern rather than a long list of forbidden foods.

Arrange medical review for persistent diarrhoea, ongoing vomiting, blood in the stool, unexplained weight loss, anaemia, fever, or symptoms that wake you repeatedly at night. Seek urgent care for severe abdominal pain, fainting, confusion, or signs of serious dehydration. A suspected intolerance should not delay assessment of these warning signs.

Which intolerance is plausible from my symptom timing? Do I need a breath test or coeliac testing before changing my diet? How long should a dietary trial last, and how should foods be reintroduced? Can I see a dietitian for a balanced plan?