Are food intolerance tests worth it, and how are IgG tests different from allergy tests?

Are food intolerance tests worth it for you — or is this an emergency?

This guide is for adults with bloating, tummy pain, headaches, tiredness or skin symptoms who are wondering whether a home "food intolerance" or "food sensitivity" kit will find the cause. For most people, it won't: the kits measure an antibody that allergy specialists say doesn't diagnose allergy or intolerance.

Call 911 or 999 now if, after eating, your lips, mouth, throat or tongue suddenly swell, breathing becomes fast or difficult, your throat feels tight, your skin or lips turn blue, grey or pale, or someone becomes confused, drowsy or faints. The NHS says to use an adrenaline auto-injector straight away if you have one, then call an ambulance even if you feel better. See our emergency page.

See a GP, family doctor or primary-care clinician rather than buying a kit if symptoms keep coming back or you already avoid lots of foods; the NHS specifically flags needing to avoid many foods to control bowel symptoms as a reason to see a GP.

What do IgG food sensitivity tests actually measure?

They measure IgG antibodies to a panel of foods. The problem is that IgG to food is normal. The British Dietetic Association says IgG antibodies to food are found in healthy people without food allergies, so the test isn't reliable. The Canadian Society of Allergy and Clinical Immunology calls food-specific IgG a marker of exposure and tolerance, and an EAACI task force concluded in 2008 that IgG4 to foods reflects repeated exposure and may indicate tolerance, not allergy or intolerance.

That's why the professional bodies advise against them:

• US: the American Academy of Allergy, Asthma & Immunology says the test has never been scientifically proven to do what it reports, and that it and other organisations recommend against using IgG to diagnose food allergy or intolerance.
• Canada: the CSACI "strongly discourages" food-specific IgG testing, and Food Allergy Canada says IgG tests aren't recommended for diagnosing allergy, intolerance or sensitivity.
• UK: the NHS says some tests you can buy that claim to diagnose food intolerance are not recommended, as there's limited evidence they give accurate results. The Advertising Standards Authority says it has yet to see consistent evidence that IgG testing is accurate or useful, and ruled against IgG test claims in 2021 and 2025.

The tests aren't cheap. The CSACI's 2012 statement put typical prices at $400–700 in Canada; kits sold today vary, but the evidence problem is the same at any price.

Food sensitivity test vs allergy test: what's the difference?

Allergy, intolerance and coeliac disease are different problems with different tests, and an IgG kit diagnoses none of them.

• Food allergy (IgE). An immune reaction that can cause hives, swelling, wheezing and, at worst, anaphylaxis. A clinician tests with a skin-prick test or a specific IgE blood test, read alongside your history. The BDA says skin-prick tests are done only under medical supervision. IgE tests can give false positives and false negatives too, which is why the ASA says they shouldn't be used as the sole diagnostic tool, and why Food Allergy Canada says a convincing history is needed alongside them.
• Food intolerance. Not an immune reaction, according to the NHS; symptoms usually start a few hours after eating and can last hours or days. Lactose intolerance is the best known: the NHS says a GP may suggest cutting out lactose to see if symptoms improve, a blood test or a hydrogen breath test.
• Coeliac disease. An autoimmune reaction to gluten diagnosed with a specific antibody blood test, which only works if you're still eating gluten; the NHS says avoiding gluten could make the result inaccurate. Our guide to coeliac testing at home explains how much gluten and for how long.

Can an IgG test do harm?

Yes, mainly through the diet changes that follow. The CSACI warns that IgG results lead to unnecessary dietary restrictions and lower quality of life, with risks of poor growth and malnutrition when children's diets are restricted. The BDA says these tests often recommend excluding many foods unnecessarily, which may increase the risk of nutritional deficiencies. If you've already cut out a whole food group such as dairy, our guide to what to test and take on a plant-based diet covers the nutrients to think about.

There's a safety risk too. The CSACI points out that someone with a genuine IgE allergy may have no raised IgG to that food, and could be wrongly reassured into eating it again.

What actually works?

1. A food and symptom diary. The NHS suggests one to help work out triggers: what you ate, when symptoms started and how long they lasted.
2. Your GP, family doctor or primary-care clinician, who can look for other causes and arrange the right test.
3. An allergy referral for skin-prick or specific IgE testing if your history suggests a true allergy.
4. A hydrogen breath test or a lactose trial if dairy seems to be the problem.
5. A coeliac blood test while you're still eating gluten.
6. A dietitian-led elimination and reintroduction diet. The BDA says elimination diets are best done under a registered dietitian. For irritable bowel syndrome, NICE says diets such as low FODMAP should only be advised by a healthcare professional with expertise in dietary management.

What's free in the US, Canada and UK?

United States

Start with a primary-care clinician, who can refer you to an allergist or gastroenterologist if needed; check your plan's network and referral rules first. Without insurance, federally funded health centres offer primary care on a sliding scale.

Canada

Seeing a family doctor or walk-in clinic is free. The Canadian Medical Association says allergy clinics generally need a referral, and coverage varies by province: skin-prick tests are often covered while blood tests often aren't, and in Alberta only the allergist consultation is covered, with patients paying for testing materials. Labs may offer allergy blood tests, but a doctor must sign the requisition.

United Kingdom

Your GP can assess you free on the NHS, arrange coeliac or lactose tests, refer you to an allergy clinic, and refer you to a dietitian if they think you have a food intolerance.

Compare your options

If you're comparing home kits for other tests, our test kit comparison lists what each measures and where it ships. Checked 20 October 2026.

What to do next

1. Any swelling of the lips or throat, or trouble breathing after food: call 911 or 999.
2. Keep a food and symptom diary for a few weeks without cutting foods out yet.
3. Book your GP, family doctor or primary-care clinician and take the diary with you.
4. Keep eating gluten until any coeliac test is done.
5. Only cut out foods with a plan, ideally with a dietitian, and reintroduce them to check.

Common questions

Related guides

• Always tired? The five blood tests worth asking for
• Do I need a multivitamin? What does the evidence say by age and diet?
• Free care routes in the US, Canada and UK

Sources

1. American Academy of Allergy, Asthma & Immunology. IgG food test. Updated May 2026.
2. Carr S, et al. CSACI position statement on the testing of food-specific IgG. Allergy, Asthma & Clinical Immunology, 2012.
3. Stapel SO, et al. Testing for IgG4 against foods is not recommended as a diagnostic tool: EAACI Task Force Report. Allergy, 2008.
4. Food Allergy Canada. Mythbuster: are food sensitivity (IgG) tests helpful for diagnosing a food allergy?
5. British Dietetic Association. Food fact sheet: food allergy and food intolerance testing. Review due August 2029.
6. Advertising Standards Authority / CAP. Health: food allergy and intolerance testing. June 2025.
7. NHS. Food intolerance.
8. NHS. Food allergy — symptoms, when to call 999, diagnosis.
9. NHS. Lactose intolerance — diagnosis.
10. NHS. Coeliac disease — diagnosis.
11. NICE. Irritable bowel syndrome in adults: diagnosis and management (CG61), recommendation 1.2.1.8.
12. NHS. IBS — diet, lifestyle and medicines; when to see a GP.
13. Canadian Medical Association. How does allergy testing work in Canada?
14. Health Resources and Services Administration. Find a health center.

General information, not medical advice — see our medical disclaimer. Written to the WhereToStart editorial policy. Next scheduled review: 20 April 2027.