Food Intolerance Testing: What the Evidence Really Says
Food intolerance tests seem to be everywhere right now - from lab-based services offered by private clinics, to home kits you can order online, and even tests popping up in gyms. As a dietitian, I’m often asked by clients whether these tests are accurate, helpful, or worth the money.
In this blog, I’ll summarise the main types of food intolerance tests, outline what the research says, review current professional guidelines, and share my perspective as a healthcare professional specialising in gut health.
What Are Food Intolerance Tests?
Most commercial food intolerance or sensitivity tests measure IgG antibodies to a variety of foods, usually using a small blood sample collected either at home or in a lab. The theory is that raised IgG levels indicate your immune system is reacting to those foods, which could cause bloating, fatigue, or skin issues.
The evidence, however, does not support this assumption. IgG antibodies are a normal part of your immune system’s response to food, so having higher levels doesn’t necessarily mean you have an intolerance or sensitivity. Research shows that these tests haven’t been properly validated or proven reliable, meaning scientists haven’t confirmed that the results accurately reflect true food sensitivities or that you would get the same result if you repeated the test.
Other tests, such as ALCAT or Mediator Release Tests (MRT), measure how white blood cells react to specific foods or chemicals, detecting the release of histamine or cytokines. While some practitioners report symptom improvements in IBS, migraines, or skin issues, scientific evidence remains limited, and major medical organisations do not endorse them.
How IgE Allergy Tests Are Different
It’s important to distinguish food intolerance tests from IgE-mediated allergy tests, the standard for diagnosing true food allergies. IgE tests (blood tests or skin prick tests) measure immediate allergic reactions. Symptoms can be rapid and sometimes severe - including hives, swelling, vomiting, wheezing, or, rarely, anaphylaxis. It’s also worth baring in mind that while IgE tests are clinically validated, a positive result does not automatically diagnose someone with an allergy. Results must be interpreted alongside a patient’s history, and actual reactions, ideally by a trained allergy specialist or immunologist.
Unlike IgE tests, IgG and mediator release tests most food intolerance tests use do not identify potentially allergic reactions, and their results cannot reliably predict symptoms. Understanding this distinction is crucial for anyone considering food testing.
Bioresonance and Other Alternative Tests
Bioresonance tests claim to detect food intolerances or sensitivities by measuring energy frequencies or antibody levels. Some analyse blood samples, while others use hair or skin samples.
The science does not support these tests:
No mechanism exists to show energy field comparisons can detect food sensitivities.
Tests often report large numbers of “problem foods,” which can be confusing or alarming.
Reviews consistently emphasise the lack of reproducible, controlled clinical trials.
These tests are generally considered unvalidated and are comparable to other alternative techniques like electrodermal (Vega) testing.
Food Intolerance Testing and IBS
While food intolerance tests are not recommended for IBS diagnosis and treatment, there is some emerging evidence suggesting potential benefits in symptom management. Earlier clinical trials suggested that IgG-guided elimination diets could reduce bloating, abdominal pain, and altered bowel habits, though results were inconsistent (Atkinson et al., 2004; Guo et al., 2012). More recently, a multicentre, randomised, sham-controlled trial published in Gastroenterology (2025) demonstrated that targeted IgG-based elimination diets led to significant improvements in abdominal pain and overall IBS symptoms, with individuals with mixed-type (IBS-M) and constipation-predominant IBS (IBS-C) benefiting most - around two-thirds achieved a ≥30% reduction in abdominal pain compared to 30% in the control group.
However, it is important to note some limitations of this study: it did not specifically control for FODMAP intake, which we know affects IBS symptoms. For example, if someone’s report came back advising them to restrict dairy and wheat than this would also significantly lower their fermentable carbohydrate intake, through reduced intake of lactose and fructans (read more about the low FODMAP diet here). This is what I believe is one of the reasons many report an improvement following use of these tests. The intervention also only lasted eight weeks, limiting insight into the long-term benefits and the sample size, was relatively small. Outcomes also relied on self-reported symptom data, which can introduce bias. I know from my clients, that many report feeling better on test-guided diets, but benefits may be due to having structured advice or simply paying closer attention to their eating patterns. These factors mean the findings, while promising, should be interpreted cautiously and not taken as definitive proof of diagnostic value.
In short, while we do not have the evidence to use IgG testing as diagnostic tool, the research gives us further insight into the psychological benefits of structured and personalised advice when approaching IBS symptom relief.
So What Do the Clinical Guidelines Say?
Health bodies are consistent in their advice:
NHS and NICE: Do not recommend commercial food intolerance tests for diagnosis. Structured elimination and reintroduction guided by dietary history remain the gold standard.
British Dietetic Association (BDA): IgG testing is not validated as a reliable diagnostic tool and should never be used alone to guide diet changes.
Allergy UK: IgG antibodies usually reflect a normal immune response, not intolerance.
My Professional Perspective
Based on the current evidence, I do not recommend microbiome or IgG-based food sensitivity testing as diagnostic tools for functional gut disorders such as IBS.
I’ve seen the downsides of using these intolerance tests, which usually result in strict dietary restriction. Often overly restrictive eating patterns lead to nutrient deficiencies, disordered eating behaviours, and even negative impacts on the gut microbiome, including reduced microbial diversity. Prolonged restriction may also impair the mucosal lining and contribute to mast cell-related immune responses, compounding symptoms rather than resolving them. In my own practice, I’ve been moving away from restrictive protocols and more towards a personalised gut-nourishing approach - emphasising dietary diversity, plant-based foods, and prebiotic-rich ingredients to help rebuild tolerance and resilience.
That said, I also recognise that for many of the clients, these tests have provided a sense of clarity and control in a space that often feels overwhelming and unpredictable. Some report meaningful improvements after using these tests, and it's important to acknowledge their experience rather than dismiss them. I would also discourage my clients from using them, but in some cases where my clients have already ordered the tests I will support them with realistic expectations, interpreting test results alongside symptoms, diet, lifestyle, and medical history - always making it clear that these tests are not definitive diagnostics.
Ultimately, my focus remains on evidence-based strategies: optimising fibre intake, encouraging diverse and minimally restrictive diets, using pre- and probiotics when indicated, and addressing key lifestyle factors such as stress, sleep, and nervous system regulation, which play a critical role in gut function (read more about a holistic approach to IBS here).
Key Takeaways
IgG and MRT tests are not diagnostic. Elevated antibodies or immune responses do not reliably indicate a food intolerance.
IgE allergy tests are different. They can detect true allergies and should be interpreted by a specialist.
Bioresonance and energy-based tests lack scientific support.
Some clients feel better with test-guided diets, often due to structured elimination, awareness of eating patterns, increased motivation to make changes due to financial investment or potentially reduced FODMAP intake.
Professional guidance is essential to ensure safety and nutritional adequacy.
Evidence-based strategies & holistic approach remain key: dietary diversity, optimum fibre intake, prebiotics/probiotics, stress management, and sleep hygiene.
References
Allergy UK. (2023). Cow's Milk Allergy in Adults. Retrieved September 3, 2025, from https://www.allergyuk.org/resources/adult-cows-milk-allergy/
Atkinson, W., Sheldon, T.A., Shaath, N. & Whorwell, P.J., 2004. Food elimination based on IgG antibodies in irritable bowel syndrome: a randomised controlled trial. Gut, 53(10), pp.1459–1464. https://doi.org/10.1136/gut.2003.037697.
British Dietetic Association (BDA). (n.d.). Food allergy and food intolerance testing. Retrieved September 3, 2025, from https://www.bda.uk.com/resource/food-allergy-intolerance-testing.html#
Guo, H., Jiang, T., Wang, J., Chang, Y., Guo, H. & Zhang, W., 2012. The value of eliminating foods according to food-specific immunoglobulin G antibodies in irritable bowel syndrome with diarrhoea. Journal of International Medical Research, 40(1), pp.204–210. https://doi.org/10.1177/147323001204000121.
National Institute for Health and Care Excellence (NICE). (2011). Food allergy in under 19s: assessment and diagnosis. Retrieved September 3, 2025, from https://www.nice.org.uk/guidance/cg116
NHS. (n.d.). Food intolerance. Retrieved September 3, 2025, from https://www.nhs.uk/conditions/food-intolerance/
Singh, P., Chey, W.D., Takakura, W., Cash, B.D., Lacy, B.E., Quigley, E.M.M., Randall, C.W. and Lembo, A., 2025. A novel, IBS-specific IgG ELISA-based elimination diet in irritable bowel syndrome: A randomized, sham-controlled trial. Gastroenterology, 168(6), pp.1128–1136.e4. https://doi.org/10.1053/j.gastro.2025.01.223
