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Intolerance testing

IgG food tests: the evidence

Why the popular IgG food intolerance tests are not recommended by allergy bodies - and what to do instead.

Key facts

At a glance

  • The claim: raised IgG antibodies against foods reveal intolerances driving fatigue, bloating and skin problems.

  • The evidence: allergy societies worldwide advise against IgG testing - food-specific IgG reflects normal exposure and tolerance, not intolerance.

  • The risk: acting on long positive lists leads to needlessly restrictive diets, expense, and occasionally genuine nutritional harm.

  • What works instead: structured elimination and reintroduction with a registered dietitian, or validated tests for specific conditions.

  • Follow-up: unexplained food-related symptoms deserve a proper assessment - coeliac screening, allergy testing or breath tests as the story dictates.

The full picture

What this test involves, and how to get it

IgG food panels - widely marketed online and in pharmacies - measure IgG antibodies against dozens or hundreds of foods and present the raised ones as intolerances. The scientific consensus is unusually clear: allergy and immunology societies across Europe, North America and Australia advise against these tests, because food-specific IgG is a normal finding that reflects what you regularly eat, and if anything correlates with tolerance rather than harm. A typical panel flags many foods in perfectly healthy people, and the lists it produces track diet, not disease. This does not mean your symptoms are imaginary - it means this particular test cannot explain them.

The evidence-based alternatives depend on the story. Immediate reactions point to proper IgE allergy testing; bloating and bowel symptoms may justify coeliac serology, lactose or fructose breath tests, or a dietitian-supervised low-FODMAP process; and the most reliable general tool remains a structured elimination diet with deliberate reintroduction, which tests cause and effect directly in your own body. These pathways are available through NHS referral or privately within days to weeks. Money earmarked for an IgG panel is better spent on a registered dietitian consultation - it answers the same question, credibly.

A quiet reminder

This guide is for information, not medical advice.

Your own clinician knows your history and can tell you which parts apply to you. Next review of this page: 2027-09-27.

Frequently asked

Common questions about IgG food tests: the evidence.

Quick, plain-English answers to what people ask us most.

  • What are IgG food tests, and what do they claim to show?

    IgG food tests measure antibodies of the IgG class against various food proteins in your blood, and are marketed as a way to identify foods that might be causing symptoms such as bloating, fatigue, or skin issues, often described as 'food intolerance' testing.

  • Why would someone consider an IgG food test?

    People often seek these tests when they have ongoing, hard-to-explain symptoms after eating and want a quick way to identify problem foods, particularly if other medical investigations have not found a clear cause.

  • What does the evidence actually say about IgG food testing?

    The scientific and clinical consensus, including from major allergy organisations, is that IgG antibodies to food are a normal, expected response to eating that food regularly, not a marker of intolerance or disease. Multiple studies have found no reliable link between IgG levels and food-related symptoms, and it is not recommended as a diagnostic tool by mainstream allergy and immunology bodies.

  • Do I need to prepare for an IgG food test?

    If you choose to have one despite the evidence limitations, it is simply a blood test with no fasting required. However, it is worth discussing with a doctor or dietitian first, given the concerns about how the results are often interpreted commercially.

  • What happens during the test?

    A blood sample is taken and sent to a lab, where it is analysed against a panel of food proteins, typically producing a long list of foods with associated antibody levels.

  • What happens if my IgG food test shows lots of 'reactive' foods?

    This is common and expected, given that IgG naturally rises with regular exposure to a food, and does not reliably indicate a problem. Acting on these results by eliminating many foods can risk unnecessary dietary restriction and nutritional gaps without addressing the actual underlying issue. Discussing symptoms with a doctor or registered dietitian, rather than relying on this test, is strongly recommended.

  • Are IgG food tests accurate or reliable for diagnosing intolerance?

    No; despite being widely marketed, they are not considered a valid or reliable method for diagnosing food intolerance by allergy specialists, and the results do not correlate well with genuine symptom improvement when tested in controlled studies.

  • How much do IgG food tests cost, and are they available on the NHS?

    They are not offered on the NHS due to the lack of supporting evidence. Private companies do sell these tests directly to consumers, and cost varies by provider where offered, though this platform recommends discussing genuine investigation options with a doctor instead.

  • What should I do instead if I suspect a food intolerance?

    A supervised elimination and reintroduction diet, ideally guided by a doctor or registered dietitian, remains the most evidence-based way to identify genuine food triggers, alongside ruling out other conditions such as coeliac disease or irritable bowel syndrome where relevant.

  • How do I get a proper assessment for suspected food-related symptoms?

    Booking a consultation with a GP, gastroenterologist, allergist, or registered dietitian is the recommended route, allowing appropriate tests and a structured, evidence-based approach rather than relying on unvalidated commercial panels.