Understanding Food Sensitivity Testing: Why Elimination Matters More Than the Lab Report

Food sensitivities and intolerances have become increasingly recognized in both clinical settings and public health conversations. With more people experiencing symptoms like bloating, fatigue, skin issues, or joint pain, it’s no surprise that commercial food sensitivity testing has exploded in popularity. However, many people are surprised—and sometimes confused—by the results. One of the most common concerns is this:

“Why did my test flag all the foods I eat regularly?”

The answer lies in how food sensitivity tests work, and why they often reflect immune exposure rather than immune intolerance. Understanding this distinction is critical for anyone trying to improve their health through dietary changes.

What Food Sensitivity Tests Actually Measure

Most commercial food sensitivity panels assess immunoglobulin G (IgG) antibodies—specifically, IgG4. These antibodies are produced by the immune system after exposure to food proteins. But here’s the catch: IgG responses are often associated with tolerance, not inflammation or allergy.

This means that when you eat a food regularly, your immune system may produce a higher level of IgG antibodies to that food—not because your body is reacting negatively to it, but simply because it recognizes it as familiar.

In fact, the European Academy of Allergy and Clinical Immunology (EAACI) states clearly:

"Testing of IgG4 to foods is not recommended for the diagnosis of food intolerance or allergy. The presence of IgG4 antibodies to foods is a normal immune response after exposure to food components."

This makes it clear that foods recently consumed—and often eaten—can test positive on a sensitivity test even if they’re not harmful.

Elimination Trials: The Gold Standard

The most practical and effective method for identifying true food sensitivities is the elimination and reintroduction protocol. This approach involves removing common or suspected trigger foods for a period of 3 to 4 weeks, then reintroducing them one at a time while monitoring for delayed reactions.

This method works because:

• It accounts for delayed hypersensitivity reactions that may not show up on antibody tests.

• It avoids false positives caused by recent consumption.

• It allows you to assess your personal response—not just your immune system’s recognition.

An elimination trial paired with symptom tracking provides a real-world, personalized method for understanding how specific foods affect your body.

Allergy, Sensitivity, and Intolerance: What's the Difference?

It's important to understand the different immune and non-immune reactions that the body can have to food.

Type	Immune Involvement	Common Tests	Timing	Common Symptoms
Food Allergy	IgE (histamine-driven)	Skin prick, RAST	Immediate	Hives, swelling, anaphylaxis, respiratory issues
Food Sensitivity	T-cell mediated, IgG/IgA	Elimination, IgG/IgA blood test	Delayed	Fatigue, brain fog, bloating, joint pain
Food Intolerance	Non-immune (enzyme-related)	Breath tests, challenge tests	Hours later	Cramping, gas, diarrhea (e.g., lactose intolerance)

The Role of T Cells in Food Sensitivities

While antibody-based tests (like IgG or IgA) get most of the attention, many food sensitivities involve the activity of T cells—a type of immune cell that coordinates inflammation and immune memory.

T cells are central to delayed hypersensitivity reactions, where symptoms may occur hours or even days after eating a problematic food. Unfortunately, T-cell reactions are not measured by standard food sensitivity tests.

This explains why someone can have a clear IgG panel but still react poorly to gluten, dairy, or other foods. Their immune system may be reacting through a cell-mediated pathway rather than an antibody-mediated one.

Why Timing Matters in Food Sensitivity Testing

If you take a food sensitivity test without modifying your diet beforehand, the results may reflect your recent eating habits more than your body’s actual sensitivities. Foods you eat often are more likely to be flagged—not because they’re harmful, but because your immune system recognizes them.

On the other hand, foods you haven’t eaten in weeks may not show up at all, even if they would trigger a reaction upon reintroduction.

This is one reason many integrative and functional medicine practitioners recommend eliminating common reactive foods (such as dairy, gluten, soy, corn, and eggs) for several weeks before testing, or using test results only in conjunction with an elimination protocol.

When Is Food Sensitivity Testing Useful?

Despite their limitations, food sensitivity tests can offer value in certain cases:

• When an individual cannot commit to a strict elimination trial.

• When symptoms are persistent and difficult to trace.

• When paired with an experienced practitioner who can interpret results in context.

These tests should be viewed as informational tools, not diagnostic conclusions.

Conclusion

Food sensitivity testing can offer clues about your immune system’s interaction with foods—but the presence of antibodies, especially IgG, often reflects routine exposure, not intolerance or danger.

For most people, a well-structured elimination and reintroduction protocol remains the most practical and accurate way to identify food sensitivities. Combining this method with a deeper understanding of the immune system—especially the role of T cells—can help you make informed decisions about your diet and long-term health.

If you’ve ever been overwhelmed by a long list of flagged foods, remember: a “positive” test result doesn’t necessarily mean a food is the problem. It may just mean your body remembers eating it.

References

1. Stapel, S. O., Asero, R., Ballmer-Weber, B. K., Knol, E. F., Strobel, S., Vieths, S., & Kleine-Tebbe, J. (2008). Testing for IgG4 against foods is not recommended as a diagnostic tool. Allergy, 63(7), 793–796. https://doi.org/10.1111/j.1398-9995.2008.01705.x

2. European Academy of Allergy and Clinical Immunology (EAACI). (2010). Position paper on the use of IgG4 testing in food allergy diagnosis.

3. Vojdani, A. (2009). The role of the immune system in the etiology of food allergy and sensitivity. Integrative Medicine, 8(5), 30–41.

4. Sicherer, S. H., & Sampson, H. A. (2014). Food allergy: Epidemiology, pathogenesis, diagnosis, and treatment. Journal of Allergy and Clinical Immunology, 133(2), 291–307. https://doi.org/10.1016/j.jaci.2013.11.020

5. Bernardi, L., et al. (2019). Immunological and clinical effects of an elimination diet in patients with food sensitivity based on IgG antibodies. Nutrition & Metabolism, 16, 17. https://doi.org/10.1186/s12986-019-0343-y