IgG food tests mostly show what you eat, not what hurts you

Key takeaways

• When CBC’s Marketplace ran two IgG food tests on the same host, one lab flagged 52 foods and the other 30, including wheat, milk and flax she ate without trouble¹.
• Allergy experts say food IgG mostly shows you’ve eaten a food, and high IgG4 may signal tolerance; U.S., Canadian and European allergy societies advise against using these tests for diagnosis²⁴⁵.
• A 2025 trial of 238 people with IBS found pain relief in 59.6% on an IgG-guided diet versus 42.1% on a sham diet, but the company Biomerica funded it and the sham group did well, too⁷⁸.
• In a 1998 study, a commercial lab retested duplicate blood samples and one patient’s results changed for 50 of 95 foods⁹.
• A better path starts with a symptom record, an allergist for any fast reaction and a planned elimination and reintroduction, rather than a 100-food panel²³¹⁴.

Charlsie Agro, a host of CBC’s consumer program Marketplace, kept track of what she ate. Then she had blood drawn for two food sensitivity tests from two Canadian lab companies, Dynacare and Rocky Mountain Analytical, which is owned by LifeLabs¹.

The results didn’t match. One lab said she was intolerant of 52 foods. The other said 30¹.

Both flagged flax, which she ate every day with no problems. Both also flagged wheat, milk, egg whites, corn, barley and kidney beans, foods she ate often without symptoms¹.

Another customer, Laura Chapnick, paid $325 for a Dynacare test after seeing an ad at one of its clinics. Her report told her to cut back on or drop 26 foods, including wheat, milk, eggs, potatoes and peanuts¹.

These tests measure IgG, a type of antibody. Allergists who spoke with CBC said high IgG mostly means a person has eaten a food, not that it’s causing harm¹.

If meals leave you feeling unwell, the appeal is easy to see: a blood test promises an answer a rushed doctor may never have offered. The science behind that promise is more mixed than either side tends to admit.

IgG is a record of meals, not a list of enemies

Antibodies are proteins your immune system makes to recognize things it has met before. Classic food allergy runs on one type, IgE. Allergists diagnose it with IgE tests read alongside your history and an exam³.

IgG works differently. Pediatric allergist David Stukus of Nationwide Children’s Hospital told CBC it’s a “memory antibody”¹. It builds up after you’ve been exposed to something.

In 2008, the European Academy of Allergy and Clinical Immunology (EAACI) laid out the science in a position paper⁵. Food IgG4, the subtype many panels measure, reflects repeated contact with food proteins. The authors saw it as a sign of tolerance, linked to immune cells that calm reactions. They found no convincing evidence that it releases histamine, the chemical behind allergy symptoms, in people⁵.

Allergy treatment points the same way. When immunotherapy works, IgG4 to the allergen rises⁵. Canada’s allergy society notes that food IgG shows up in people going through oral immunotherapy, a supervised treatment meant to build tolerance to a food⁴.

Healthy people test positive, too. EAACI described 13 healthy lab workers who all had positive food IgG4 results, matching neither their allergy tests nor any symptoms⁵. Studies of schoolchildren and infants also found these antibodies common. Changing diets based on them, the authors warned, would mean massive overtreatment⁵.

Most panels test 90 to 100 foods². Because IgG tracks exposure, a report can light up for the foods you eat most, which fits what happened to Agro¹⁵.

Allergy societies on three continents reached the same verdict

First, the case as sellers make it. Test companies and some practitioners say cutting high-IgG foods can ease many symptoms. Some websites link these diets to relief from IBS, autism, rheumatoid arthritis and epilepsy². In a written response to Marketplace, LifeLabs said a test doesn’t need to be diagnostic to be clinically useful, and cited journal studies on the benefits of removing IgG-reactive foods¹.

The major allergy societies have looked at that case and disagree:

• Europe. EAACI’s 2008 paper called IgG4 testing irrelevant for diagnosing food allergy or intolerance and said it shouldn’t be done for food complaints⁵.
• United states. The American Academy of Allergy, Asthma & Immunology (AAAAI) endorsed EAACI’s position in 2010 and recommends against IgG testing for food allergy, intolerance or sensitivity². Its page, updated in May 2026, says the test has never been proven to do what it claims, and that much of the supporting research is outdated or didn’t use the test being sold².
• Choosing Wisely. In 2012, AAAAI told clinicians not to use unproven tests such as IgG in allergy workups³.
• Canada. The Canadian Society of Allergy and Clinical Immunology (CSACI) firmly discouraged the testing in its 2012 position statement and said it doesn’t support physicians or pharmacists offering it⁴.

Regulators have weighed in, too. Health Canada has licensed some IgG tests, but none is meant to diagnose food intolerance on its own¹. In 2021, Britain’s advertising watchdog said it hadn’t seen solid evidence that IgG tests reliably identify intolerances, or that diets based on them ease symptoms¹³. It pointed to its past rulings on ads for an IgG test from YorkTest, for electrodermal testing and for hair analysis¹³.

In the U.S., we didn’t find a Federal Trade Commission case aimed squarely at these tests.

The trials sellers point to, read closely

Sellers do have studies: two randomized trials in irritable bowel syndrome (IBS) found effects worth a close look.

The 2004 British trial. Researchers published a study in the journal Gut of 150 IBS outpatients who took an IgG test⁶. Half were randomly assigned to a “true” diet that cut their positive foods. The other half got a sham diet that cut the same number of different foods. Neither patients nor staff knew who got which, and the diets lasted 12 weeks⁶.

Symptom scores fell 100 points on the true diet and 61.5 points on the sham diet. The 39-point gap was described as a 10% greater drop. Among patients who stuck to the diet fully, the gap was 26%⁶.

Now the fine print. YorkTest Laboratories ran the blood tests and wrote the diet sheets⁶. More people quit the true diet, 24 versus 13, most of them because it was hard to follow⁶.

The two diets also cut very different foods. True diets most often dropped yeast (87% of patients), milk (84%), egg (57%) and wheat (49%). Sham diets most often dropped potato (61%), rice (55%) and tomato (44%)⁶. So was it the antibodies, or simply the foods?

The trial can’t say. EAACI later noted that an IgG-guided IBS trial had been challenged over its design⁵.

The 2025 U.S. trial. A World Gastroenterology Organisation commentary calls it the largest study in the field⁸. Prashant Singh of Michigan Medicine and colleagues at eight centers enrolled 238 adults with IBS who tested positive for at least one food on an 18-food IgG panel built for IBS⁷⁸. For eight weeks, they followed either a diet guided by their results or a sham diet⁷.

The goal was a drop in belly pain of at least 30% for two of the last four weeks. That happened for 59.6% on the guided diet and 42.1% on the sham⁷⁸. The gap was bigger in IBS with constipation (67.1% vs. 35.8%) and in mixed-type IBS (66% vs. 29.5%)⁷⁸.

The company Biomerica funded the trial, and several authors disclosed ties to it⁷. The WGO reviewer pointed to a high placebo-style response of about 40%, lower adherence on the guided diet and dropouts, and said more data are needed⁸. The authors themselves called for a larger study⁷.

What this does and doesn’t show:

• It tested a narrow IBS panel against belly pain, not a 100-food panel for fatigue, brain fog or weight²⁷.
• About 4 in 10 people on a sham diet improved, so feeling better after cutting foods doesn’t prove the test picked the right ones⁷⁸.
• It’s a lead for IBS research, not proof that consumer panels work.

Same blood, different answers

A test that can’t agree with itself can’t guide your plate. In a small 1998 study, researchers sent duplicate blood samples from nine people with suspected food intolerance to a commercial lab, without telling the lab⁹. It measured IgE and IgG4 to 95 foods.

Agreement was poor. On kappa, a measure of agreement beyond chance where 1 is perfect, results never topped 0.51⁹. Eight of the nine people had more mismatches than the researchers had set as acceptable, and one person’s results changed for 50 of 95 foods⁹.

CBC found the same problem across labs¹. Clinical epidemiologist Jason Busse told the program that the studies companies cited were very problematic¹. Stukus added that IgG can cross-react between similar foods, so one food can make a related one look guilty¹.

Cells, currents, hair and muscles: the other tests

Electrodermal testing reads the skin’s response to small electrical currents¹². In a 2001 BMJ study, University of Southampton researchers tested 30 volunteers, half allergic to dust mites or cats and half not. Each had 54 blinded Vega tests¹⁰. The device couldn’t tell allergic people from the others¹⁰.

It tested environmental allergies, not foods¹⁰. A British primary care allergy guide notes that no studies have evaluated Vega testing for food allergy¹¹.

Hair analysis failed on consistency, with matched hair samples giving different results¹¹. Applied kinesiology, or muscle testing, has no evidence of accuracy¹¹. ALCAT, one of several tests that look for changes in white blood cells, was found ineffective in controlled trials¹¹¹².

Here’s our guide to what you may be offered.

Test	What it measures	Validated for	Verdict
Food IgG or IgG4 panel	Antibodies to 90 to 100 foods2	Not validated to diagnose allergy or intolerance245	Skip for diagnosis
IBS-specific IgG panel (research)	IgG to 18 foods7	One industry-funded trial for IBS pain78	Not ready; watch for larger trials
IgE blood test or skin prick test	Allergy antibodies3	Food allergy, read with your history314	Useful with an allergist
Supervised oral food challenge	Your reaction to measured doses of the food14	The gold standard for IgE food allergy14	The best answer
ALCAT or cytotoxic test	Changes in white blood cells12	Found ineffective in controlled trials11	Skip
Mediator release test (MRT)	Release of inflammatory chemicals in a blood sample12	No independent validation we could find	Skip until tested
Electrodermal (Vega)	Skin’s electrical response12	Failed a blinded allergy trial10	Skip
Hair analysis	Minerals in hair12	Matched samples disagreed11	Skip
Applied kinesiology or NAET	Muscle strength while holding a food12	No evidence of accuracy1112	Skip

What a wrong answer can cost

Money. CSACI put typical Canadian prices at $400 to $700 in 2012, and CBC found tests in Canada from just over $100 to nearly $400¹⁴.

Nutrition. Needless cutting brings unnecessary restrictions and a lower quality of life, CSACI warns. In children, it can mean poor growth and malnutrition⁴. A registered dietitian told CBC that the diet changes on Chapnick’s report put her health at risk¹.

False reassurance. This is the most dangerous mistake. Someone with a true IgE allergy may show no high IgG to that food, CSACI notes, and could be told to bring back a food that might cause a severe reaction⁴.

New problems. In some children, cutting foods has come before new allergic reactions, as our article on medically appropriate elimination diets explains. A shrinking list of safe foods can also feed fear around eating.

If food rules have started to feel frightening, or your list of safe foods keeps shrinking, call the National Alliance for Eating Disorders helpline at 1-866-662-1235. If you’re in crisis, call or text 988.

A better path when you suspect a food

This is a route that takes both your symptoms and the evidence seriously.

1. Rule out warning signs first. See the box below.
2. Write it down. For two weeks, note what you ate, when symptoms started and how long they lasted. Our articles on symptom diaries show how.
3. Sort fast reactions from slow ones. If a food has ever caused a reaction soon after eating, see an allergist before any test or diet change. Expect IgE testing guided by your history, and a supervised food challenge if the answer is unclear³¹⁴.
4. Check gluten the right way. If wheat is a suspect, our celiac article explains why the blood test comes before cutting gluten.
5. Ask about targeted tests. Some tests answer one clear question, such as whether you digest lactose. Our article on food intolerances covers them.
6. Run a short, planned elimination. With a dietitian, cut one food group, set an end date, then bring it back and watch what happens. For IBS, ask about a guided low-FODMAP trial, covered in our low-FODMAP article.
7. Already have a panel? Don’t cut everything on it. AAAAI advises getting proper advice, such as from an allergist, before you overhaul your diet². If you’ve already dropped foods you used to eat without trouble, ask about bringing them back.

Trust your body’s signals, then test them fairly

Natural-health readers are right that food matters and that people react to it differently. Medicine agrees, and uses elimination diets for some conditions. The problem is the shortcut, not the instinct.

Skepticism should run in every direction. In Canada, these panels are sold by mainstream lab companies, not just wellness clinics¹. And one of the clearest tests of electrodermal devices came from complementary medicine researchers, partly funded by the device’s maker, who published a negative result anyway¹⁰.

Your body is a better guide than a 100-food printout, as long as you test it carefully. Change one thing at a time, set an end date and bring foods back to see what’s really going on.

How strong is the evidence?

Claim	Rating	Why
IgG panels identify the foods causing your symptoms	Evidence says no, or unsafe	Societies advise against; healthy people test positive; poor repeatability2459
Food IgG mainly reflects eating a food, not harm from it	Strong evidence	Found in healthy people; rises with repeated exposure and successful immunotherapy25
An IgG-guided diet eases IBS pain	Promising but early	Two sham-controlled trials, both tied to test companies, with high sham response678
Electrodermal testing diagnoses allergies	Evidence says no, or unsafe	Failed a blinded trial10
Hair analysis, muscle testing or ALCAT find food problems	Evidence says no, or unsafe	Poor consistency or failed trials; no accuracy shown11
MRT finds food sensitivities	Not enough evidence	We found no supporting studies; an allergy group lists it as a test to avoid12
IgE testing plus history, with a food challenge when unclear	Strong evidence	The accepted standard for food allergy314

Questions readers ask

The bottom line

IgG food panels measure something real, but it’s mostly a record of what you’ve eaten. Allergy societies in the U.S., Canada and Europe advise against using them to diagnose food problems, and repeat testing has produced inconsistent results.

The 2025 IBS trial is worth watching, with its industry funding and large sham response in mind. For now, the best way to find a problem food is slower and cheaper: write down your symptoms, see an allergist for fast reactions, and test one food at a time with a clear plan to bring it back.

Related reading

• Elimination diets are real medicine for some conditions and a risk for others
• When the company reading your labs also sells the fix
• Most food intolerances come down to dose, while gluten sensitivity remains a puzzle
• A roadmap from test to table for celiac disease, which most people who have it don’t know
• How to keep a gut diary, because the last meal may not be the culprit

Sources

1. CBC News, Marketplace. “‘There Is No Validity’: Unproven Blood Tests for Food Sensitivity Widely Offered in Canada.” Canadian Broadcasting Corporation. cbc.ca
2. American Academy of Allergy, Asthma & Immunology. “IgG Food Test.” AAAAI, updated May 12, 2026. aaaai.org
3. American Academy of Allergy, Asthma & Immunology. “Five Things Physicians and Patients Should Question” (Choosing Wisely list). April 4, 2012. aaaai.org
4. Carr S, Chan E, Lavine E, et al. “CSACI Position Statement on the Testing of Food-Specific IgG.” Allergy, Asthma & Clinical Immunology, 2012;8:12. aacijournal.biomedcentral.com
5. Stapel SO, Asero R, Ballmer-Weber BK, et al. “Testing for IgG4 Against Foods Is Not Recommended as a Diagnostic Tool: EAACI Task Force Report.” Allergy, 2008;63:793–796. parsemus.org
6. Atkinson W, Sheldon TA, Shaath N, Whorwell PJ. “Food Elimination Based on IgG Antibodies in Irritable Bowel Syndrome: A Randomised Controlled Trial.” Gut, 2004;53(10):1459–1464 (White Rose repository). pubmed.ncbi.nlm.nih.gov
7. HealthDay. “IgG-Guided Elimination Diet Beneficial for Irritable Bowel Syndrome” (report on Singh P, et al., Gastroenterology, 2025). February 20, 2025. healthday.com
8. Tulewicz-Marti E. “Is There a Place for an IgG Antibody-Based Elimination Diet in Irritable Bowel Syndrome?” (commentary on Singh P, Chey WD, Takakura W, et al., Gastroenterology, 2025;168:1128–36). World Gastroenterology Organisation, News You Can Use. worldgastroenterology.org
9. “Unreliability of IgE/IgG4 Antibody Testing as a Diagnostic Tool in Food Intolerance.” Clinical and Experimental Allergy, 1998;28(12), DOI 10.1046/j.1365-2222.1998.00367.x (Weill Cornell Medicine record). doi.org
10. Lewith GT, Kenyon JN, Broomfield J, et al. “Is Electrodermal Testing as Effective as Skin Prick Tests for Diagnosing Allergies? A Double Blind, Randomised Block Design Study.” BMJ, 2001;322:131. pubmed.ncbi.nlm.nih.gov
11. Choudhury D, Royal College of General Practitioners allergy representative. “Choosing Wisely: Alternative Tests.” Hosted by the British Society for Allergy & Clinical Immunology, 2020. bsaci.org
12. Kids With Food Allergies, a division of the Asthma and Allergy Foundation of America. “Unproven Methods of Food Allergy Tests.” Updated April 2024. kidswithfoodallergies.org
13. Committee of Advertising Practice and Advertising Standards Authority (UK). “Food Intolerance and Allergy Testing: Some Top Tips on Making Sure the ASA Tolerates Your Ads.” September 16, 2021. asa.org.uk
14. “Unproven Diagnostic Tests for Food Allergy.” Immunology and Allergy Clinics of North America, February 2018 (abstract). read.qxmd.com
15. American College of Gastroenterology. “Irritable Bowel Syndrome” (patient information). Updated February 2026. gi.org