Do Food Sensitivity Tests Actually Work? What Doctors Won't Tell You

Food sensitivity testing has become a massive industry. Companies like Everlywell, YorkTest, and dozens of others sell at-home blood test kits that promise to identify your food triggers with a simple finger prick. Just mail in a blood sample, wait a few days, and get a color-coded report telling you which foods to avoid.

It sounds appealing. Who wouldn’t want a definitive answer to “what’s making my stomach hurt?” But there’s a problem: the science behind these tests is far weaker than the marketing suggests.

How food sensitivity blood tests work

Most commercial food sensitivity tests measure Immunoglobulin G (IgG) antibodies to specific food proteins. The idea is that elevated IgG levels to a particular food indicate that your immune system is reacting to it, which supposedly causes symptoms like bloating, fatigue, headaches, or skin problems.

You get back a report showing IgG levels for 50-200 foods, typically rated green (low), yellow (moderate), or red (high). The implication is clear: avoid the red foods, minimize the yellow ones, and your symptoms should improve.

The problem is that this interpretation contradicts what immunologists actually know about IgG antibodies.

What the medical community says

The European Academy of Allergy and Clinical Immunology (EAACI) issued a position statement specifically warning against IgG testing for food intolerance. Their conclusion: IgG antibodies to foods are a normal physiological response to eating, not a marker of sensitivity or intolerance.¹

The American Academy of Allergy, Asthma & Immunology (AAAAI) agrees: “IgG and IgG subclass antibody tests for food allergy do not have clinical relevance, are not validated, and should not be performed.”²

The Canadian Society of Allergy and Clinical Immunology published similar guidance, stating that “the use of food-specific IgG testing to guide dietary elimination is not recommended.”³

Why the unanimity? Because IgG antibodies to foods develop naturally as part of normal immune tolerance. Finding IgG antibodies to wheat in your blood doesn’t mean wheat is a problem — it means you’ve eaten wheat. In fact, higher IgG levels to a food may actually indicate better tolerance, not worse.¹

The accuracy problem

Stapel et al. tested the reproducibility of commercial IgG food sensitivity tests by sending identical blood samples to the same lab twice. The results were inconsistent — the same person’s blood produced different “sensitivity” profiles on different days.⁴

Lavine systematically reviewed IgG testing studies and found no convincing evidence that IgG antibody levels predict food-related symptoms in the general population. The few studies showing positive results had significant methodological limitations.⁵

One often-cited study by Atkinson et al. did find benefit from IgG-guided elimination in IBS patients. However, the improvement was modest (10% greater than placebo), and the authors themselves noted that the mechanism was unclear — it could have been the general dietary changes rather than specific IgG-identified foods.⁶

Why people think they work

If the science is this weak, why do so many people swear their food sensitivity test changed their life? A few reasons:

Placebo effect and confirmation bias. If you pay $200 for a test and follow its recommendations, you’re psychologically invested in it working. You’re also more likely to notice symptom improvement and less likely to notice when symptoms persist.

General dietary improvement. Most food sensitivity reports flag common junk food ingredients — dairy, gluten, sugar, processed foods. When people eliminate these based on test results, they often feel better. But that improvement comes from eating better overall, not from avoiding their specific “sensitivities.”

The elimination effect. Any elimination protocol can provide temporary relief for someone with gut issues, regardless of which foods are eliminated. Reducing dietary variety reduces the total fermentable load on the gut, which reduces symptoms.⁷

What actually works: the elimination diet

If IgG testing is unreliable, how do you actually identify food triggers? The gold standard in gastroenterology is the elimination diet with systematic reintroduction.

The protocol is straightforward: remove commonly problematic foods for 2-6 weeks, then reintroduce them one at a time while monitoring symptoms. This approach has been validated in multiple randomized controlled trials.

Halmos et al. demonstrated that a structured low-FODMAP elimination diet reduced symptoms in 70% of IBS patients.⁸ Nanda et al. showed that systematic elimination and rechallenge identified specific food triggers in 48% of participants — triggers that were confirmed on blinded re-exposure.⁹

The key advantage of elimination diets over blood tests is that they measure what actually matters: your symptomatic response to specific foods in real-world conditions. A blood test measures antibodies in isolation. An elimination diet tests the entire chain: digestion, absorption, fermentation, motility, and nerve sensitivity.

The reintroduction advantage

Blood tests give you a static snapshot that can’t distinguish between true triggers and normal immune exposure. Elimination-reintroduction gives you dynamic, real-time data.

Van den Houte et al. ran a blinded FODMAP reintroduction trial and found that structured rechallenge identified individual triggers that patients couldn’t have identified through testing or guesswork alone.¹⁰

Böhn et al. showed that patients who completed the full elimination-reintroduction protocol ended up needing to avoid only 2-4 specific foods long-term — far fewer than what most blood test reports would suggest eliminating.¹¹

When blood testing makes sense

Not all food-related testing is worthless. Specific, validated tests exist for:

• Food allergies (IgE-mediated) — skin prick tests and specific IgE blood tests are well-validated for detecting true allergic responses
• Celiac disease — anti-tissue transglutaminase (tTG-IgA) antibodies are highly accurate
• Lactose intolerance — hydrogen breath tests measure actual malabsorption
• Fructose malabsorption — also detectable via breath testing

The issue is specifically with IgG-based “sensitivity” testing, which lacks the validation and clinical utility of these other tests.

The bottom line

• IgG food sensitivity tests are not recommended by any major allergy or immunology organization
• IgG antibodies to foods are a normal immune response, not a marker of intolerance
• Test reproducibility is poor — the same blood can produce different results
• People improve on test-guided diets mostly because of general dietary changes, not specific trigger identification
• Elimination diets are the gold standard for identifying individual food triggers, validated in multiple RCTs
• Structured reintroduction provides the real answers — testing your actual response to real food

If you’re struggling with digestive symptoms and want to identify your triggers, the evidence strongly favors a systematic elimination-reintroduction approach over a blood test kit. It takes more effort, but it produces results that are actually tied to your symptoms rather than to antibody levels of questionable clinical relevance.

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