Do Food Sensitivity Kits Really Work?

Digestive distress is common. About two-thirds of U.S. adults surveyed said they had experienced gastrointestinal symptoms over the past week, according to research in the American Journal of Gastroenterology. Reflux, bloating, abdominal pain, diarrhea, constipation and nausea can make you feel terrible throughout the day, and you deserve to get to the bottom of it.

It can be tempting to reach for an at-home food sensitivity test for answers. These are promoted as easy ways to determine exactly what your body is sensitive or intolerant to, and the idea is that you'd then cut these foods out of your diet and feel better. But do the tests really work? We'll unpack what these tests are, how you use them and if you can trust the results.

What's the Difference Between Food Allergy, Sensitivity and Intolerance?

Food allergies, sensitivities and intolerances are not the same. The most serious issue is a food allergy, which happens when the immune system detects a food protein as harmful and creates antibodies called immunoglobulin E (IgE) to fight it off. "Consuming even very small amounts of trigger foods can cause symptoms ranging from mild to life-threatening," says Patsy Catsos, RDN, a medical nutrition therapist in Portland, Maine. The most severe food allergy reaction is anaphylaxis, which can cause dangerous breathing problems and a drop in blood pressure.

A food can bother you even if you aren't allergic to it, and that's where sensitivities or intolerances can be a problem, even though their effects are potentially less dire. "Food intolerances, which don't involve the immune system, are the result of incomplete digestion or absorption of a food," Catsos says. "They cause gastrointestinal symptoms, and eating larger portions of the food in question tends to produce more significant symptoms."

Finally, there's the murkier world of food sensitivities, a term for which there is no medical definition or standard diagnosis. "They're in a bit of a grey area," Catsos says. "They involve other parts of the immune system, though not IgE antibodies. They can sometimes be managed by eating smaller portions of the food, but not always," she explains.

What Is a Food Sensitivity Test?

If you're suffering from gas, diarrhea, bloating or other unpleasant digestive issues, it can be tempting to reach for an at-home test for answers. These tests can easily be ordered online.

The majority of these tests require you to provide a sample of blood, saliva or hair. When you send back the sample, it's then analyzed against as many as 100 foods to provide a report of so-called "problem" foods. At least, that's the claim, but many experts have concerns.

Chief among them: Food sensitivity tests measure immunoglobulin G (IgG) antibodies. "IgG antibodies are not an established marker for food issues," explains Tamara Duker Freuman, a New York-based registered dietitian who specializes in digestive disorders. The presence of IgE is an indication of an allergy, but IgG is what's known as a "secondary response." Therefore, IgG doesn't prove an allergy, as you can have positive IgG from previous exposure to that food.

"Because IgG is a 'memory antibody,' the results likely measure which foods you've been eating most often. If you eliminate the foods they indicate, and you're then retested, you'd very likely get different results," says Duker Freuman. Ironically, IgG antibodies are more likely a marker of food tolerance rather than intolerance, she says. A recent study concurs: Researchers concluded that the tests "are largely misleading to the consumer and provided by unaccredited laboratories using controversial methodology."

Registered dietitian Beth Rosen, based in Southbury, Connecticut, who practices nutrition for gastrointestinal disorders and disordered eating issues, also gives two-thumbs-down to these tests, noting that the major professional allergy organizations in Europe, Canada and the United States have all issued statements opposing IgG testing. "It is important to understand that this test has never been scientifically proven to be able to accomplish what it reports to do," writes the American Academy of Allergy, Asthma & Immunology on its website, noting that the research that these testing companies show as proof that their methods work is based out outdated data in non-reputable journals and may not even be based on the test they use. In addition, a World Allergy Organization Journal position paper in 2020 listed IgG antibody panels as an unproven diagnostic approach, noting that healthy folks produce these antibodies to foods that they're not allergic to.

Another problem with the at-home tests is understanding the data they provide. Some people make drastic changes to their diets and lifestyles based on their results, which can be a mistake. The experts we consulted warned about how the tests could contribute to restrictive or unhealthy eating. "Don't self-diagnose based on one of these tests," warns Marlisa Brown, a registered dietitian who practices in Deer Park, New York. "You really need to consult with a professional to interpret the results."

What's more, the results may be confusing, and may present you with a list of foods that are now off-limits that were cornerstones in your diet before. "If you suspect a sensitivity, trust your own observations more than one of these tests," Catsos says. She suggests conducting a short elimination diet and then re-introducing suspected foods in small but increasing amounts. "Try to work out an acceptable portion of the food so you can enjoy it to at least some extent," she says.

Duker Freuman suggests keeping a food-and-symptom diary. "If you need an unbiased assessment of what you're noticing in the diary, visit a registered dietitian—one who doesn't market food sensitivity testing or sell supplements," she advises.

Bottom Line

"Many people are looking for a food culprit to blame for vague symptoms like intestinal issues, fatigue or mood issues. Sometimes there is one, and sometimes the problem isn't a specific food sensitivity so much as an overall dietary balance issue, for example," says Duker Freuman. If you wonder if a particular food is to blame, it's a good idea to work with a health care provider, such as a registered dietitian who specializes in GI issues, or a gastroenterologist, to explore possible root causes. They can also walk you through doing an elimination diet, if necessary, safely and effectively.