At-home food sensitivity tests have become increasingly popular, but how accurate and credible are the results? Writing for the New York Times, Alice Callahan explains how these tests work and what you can (and cannot) learn from them

Defining food sensitivity

According to David Stukus, director of the Food Allergy Treatment Center at Nationwide Children's Hospital, food sensitivity is typically heard in marketing rather than in medicine. "There really is no consensus definition of what a food sensitivity is," Stukus said.

Companies that sell food sensitivity tests often define food sensitivity as specific foods that cause digestive issues, gut inflammation, abdominal pain, bloating, or headaches. "Symptoms may appear hours or even days after eating, and often resolve when the offending food is avoided," Callahan writes.

Notably, a food intolerance or sensitivity is not the same as a food allergy, which triggers an immune reaction to specific foods that can lead to severe symptoms, including vomiting, hives, shortness of breath, or anaphylaxis.

What you need to know about food sensitivity tests

At-home food sensitivity test kits can be ordered online or purchased over the counter without a prescription or doctor visit.

Tests typically require users to mail a sample of several hairs or a drop of blood for testing. Within a few days or weeks, users will receive digital results, which include a list of foods that could trigger their symptoms.

While some tests claim to gauge food sensitivity to hundreds of ingredients by measuring the "bioresonance" of a person's hair, others detect the levels of IgG antibodies in the blood.

According to John Kelso, an allergist at Scripps Clinic Carmel Valley, there are also other blood tests called Alcat and MRT tests, which require users to get their blood drawn from a lab and measure the change in the size of a person's blood cells after they are exposed to food extracts in a test tube.

Currently, there are no validated tests for food intolerances or sensitivities, according to Tamara Duker Freuman, a registered dietitian at New York Gastroenterology Associates. Ultimately, the only way to determine whether a person is sensitive to certain foods or ingredients is to observe their symptoms before and after eliminating a food from their diet, Freuman noted.

"This can be a slow process involving trial and error, and the companies selling food-sensitivity tests market them as a shortcut," Callahan writes. "But medical organizations, including those in the United States, Europe and Canada, have recommended against using food sensitivity or intolerance tests because there is no good evidence that they work."

"There isn't anything in your hair that would tell you anything about your sensitivity to food," Kelso said.

In addition, the antibodies measured in IgG tests are produced during the immune system's normal reaction to food. According to Stukus, they have not been proved to correlate with symptoms or intolerances. "It's really just a reflection of what you've eaten," he added.

According to the American College of Gastroenterology's 2021 clinical guidelines for the management of irritable bowel syndrome, "[m]ultiple tests are marketed to diagnose food intolerances; however, none have been validated, and most have not been subjected to rigorous, blinded trials."

Separately, Elaine Byers, chief technical director of 5Strands Affordable Testing, a company that sells food intolerance tests that rely on a hair sample, said that "[their product] is an entry level test which will allow consumers to take a proactive approach to personal wellness. It was not designed as a diagnostic tool."

What experts are saying

Frances Onyimba, a gastroenterologist and assistant professor of medicine at the University of Maryland School of Medicine, said these food sensitivity tests can lead people to unnecessarily avoid a wide range of foods, which can cause nutrient deficiencies.

The tests can also trigger food-related anxiety, which can cause eating disorders, according to Stukus. "People come to me saying that they can't eat 15 to 20 different foods because of some unvalidated test, and it is very challenging to get them to understand why that's not the case," he said.

So far, FDA has not evaluated any of the food sensitivity tests on the market today, according to James McKinney, a press officer for the agency.

Lin Chang, a gastroenterologist and professor of medicine at the David Geffen School of Medicine at the University of California, Los Angeles, advises individuals to visit their health care provider if their symptoms are interfering with daily life, adding that symptoms are sometimes unrelated to food sensitivity. "Abdominal pain can mean pancreatic cancer, it can mean I.B.S., it can mean I ate spicy food," Chang said.

According to Freuman, some of her patients are surprised to learn their symptoms are likely the result of constipation when they believed they had a food sensitivity.

Ultimately, Stukus emphasized that a simple test cannot usually determine a patient's diagnosis. "We don't just do a bunch of tests and then see what the tests show," he said. (Callahan, New York Times, 9/13)