The widely sold ones, honestly, no. IgG blood tests — the £70–£250 kits sold online and on the high street — measure antibodies that healthy people produce as a normal response to foods they eat, so results largely reflect your diet, not your intolerances; the NHS, NICE and UK allergy bodies including BSACI and Allergy UK advise against using them. Hair tests have no scientific basis at all. The tests that ARE accurate are specific: hydrogen breath tests for lactose intolerance, blood serology for coeliac disease, and a structured elimination-and-reintroduction diet — the actual gold standard — for everything else.

An allergy is an immune (IgE) reaction — usually rapid, sometimes severe, occasionally life-threatening — and it can be tested reliably with skin prick tests and specific IgE blood tests. An intolerance doesn’t involve that immune pathway: it’s typically slower, milder and digestive (bloating, discomfort, fatigue), caused by things like enzyme deficiencies (lactose) or gut sensitivity, and there is no single blood test that can diagnose it. If your reactions are rapid — hives, swelling, lip tingling, breathing problems — you need allergy testing, not intolerance testing.

Not the IgG kind — and that’s informative in itself: the NHS doesn’t offer IgG food intolerance testing because the evidence doesn’t support it. What your GP CAN order free, when symptoms warrant it, are the validated tests: coeliac serology, lactose investigation, calprotectin (to check for inflammatory bowel disease), allergy referral where an allergy is suspected, and dietitian referral for a supervised elimination diet. Going private buys speed on those same validated routes — not access to better tests.

No. Hair contains no information about how your digestive or immune system responds to foods, and the ‘bioresonance’ methods many hair-test kits use have no scientific basis — results are effectively random. They’re cheap (£20–£80), which is part of the appeal, but a random food list can lead to unnecessary restriction while missing real triggers. Between hair and IgG blood tests, blood at least measures something real (exposure) — but neither can diagnose an intolerance.

A structured elimination and reintroduction diet — the method dietitians and the NHS actually use. Keep a food and symptom diary for 1–2 weeks, remove the suspected food (or follow a structured protocol like low-FODMAP for IBS-type symptoms) for 2–6 weeks, then reintroduce foods one at a time while tracking symptoms. Reintroduction is the diagnostic step most people skip and the reason professional support helps: a registered dietitian keeps the diet nutritionally safe and the conclusions honest. It costs little or nothing and outperforms any kit.

Yes — this is the most practically important rule on this page. The coeliac blood test (tTG-IgA) only works if you’re eating gluten regularly at the time; go gluten-free first and the test can miss genuine coeliac disease, which needs a proper diagnosis and lifelong management. If bread and pasta seem to be a trigger, test before you eliminate. The test is free via your GP or around £40–£100 privately.

Not the kits — self-requested IgG and hair tests are wellness screening with no clinical endorsement, so insurers won’t fund them. What insurance CAN cover is the proper investigation of persistent gut symptoms: GP access, consultant gastroenterology referrals, validated diagnostics like breath tests and endoscopy, and — on some policies — dietitian support, all with referral and pre-authorisation. If symptoms are genuinely affecting your life, that clinical pathway is the insurable route.