Food sensitivities affect between 20 and 60 percent of people and can occur as a reaction to pretty much any food or chemical except salt, water, and baking soda (aka bicarbonate), since these are part of the body’s make-up. “The most common food sensitivities seem to be the foods we eat most frequently—thus corn, soy, wheat, and dairy,” says Jan Patenaude, R.D., C.L.T., director of medical nutrition for Oxford Biomedical Technologies, the company that makes the Mediator Release Test (MRT) food sensitivity test.

Food sensitivities are different from food allergies and intolerances. Both food allergies and sensitivities are overreactions of the body’s immune system. “But that’s where the similarities end and the differences begin,” says Ryan Whitcomb, R.D., C.L.T., a dietitian in Jersey City, New Jersey. Whereas food allergies involve immunoglobin E (IgE) antibodies, which your body produces in excess when it overreacts to an allergen, food sensitivities involve overreactions to several types of antibodies, including immunoglobin G (igG) and/or immunoglobin M (igM). The immune system’s T cells or complement proteins may be involved. When an overreaction happens, it can cause inflammation in your body and symptoms such as migraines, congestion, or diarrhea. And food intolerances have nothing to do with the immune system—they happen when your body is missing a specific enzyme needed to process a food.

Food sensitivities are typically caused by exposure—often overexposure—to a food or chemical. But it could have nothing to do with what you eat. “It may be caused by the mother’s microbiotia during pregnancy,” says Patenaude. Some experts believe that certain cases of infant eczema may be caused by food sensitivities.

While food allergies may be life threatening, food sensitivities aren’t. They are, on the other hand, annoying and can significantly decrease quality of life by causing symptoms like headaches, abdominal pain, and brain fog. “Over time, people learn to cope with their issues—whether a stuffy nose, a funny stomach, or fatigue—because they’ve had them for as long as they can remember,” notes Whitcomb. These symptoms can take anywhere from 45 minutes to three days to show up. And then there’s the chance that you might not have any symptoms if you eat a small amount of a food. “If you’re sensitive to apples, the apple juice in the granola bar you eat might not cause an adverse reaction, but eating an entire apple might,” says Whitcomb.

Food sensitivities may be to blame, at least partially, on technology. “The technical and agricultural revolution is definitely [moving] too fast for our body’s evolution,” says Mark Pasula, Ph.D., an immunologist who created two of the major food sensitivity tests. “Our immune system is not evolving as fast as technology.”

How to Get Tested for Food Sensitivities

There are a handful of food sensitivity blood tests out there, including the IgG Food Antibodies Assessment, the Antigen Leukocyte Antibody Test (ALCAT), and the MRT. The latter is considered the best of these tests.

Several decades ago, Pasula moved from Poland to the United States. “After a few years of living here, I developed very strange allergy-like symptoms that were very, very difficult for me to cope with,” he says. “I decided to help myself and create a test that would identify my problems.” After years of experimentation, Pasula patented his first test, the ALCAT, in 1982. That test worked by identifying white cell reactions to food extracts. But Pasula calls it a “first attempt,” noting it worked decently but not as well as the next generation, the MRT, which tests not just if the blood reacts to a food or chemical—but how and to what degree the body dislikes the food. “The ALCAT test is still around, but it represents very old technology, versus today’s test,” says Pasula.

As for the IgG test, Pasula says it shouldn’t even be on your radar. “The IgG test is generally tells you which foods you consume,” he says. “If you, for instance, eat beef every day, the test very likely will show a high level of IgG to beef.” Authors of a position paper in the journal Allergy agree with this, stating that IgG testing is not helpful for determining food sensitivities.

Related: Is Personalized Nutrition the Future of Dieting?

Depending on where you live, testing with nutritional counseling could cost a few hundred dollars or more—and sometimes will be covered partially or fully by insurance. Anyone who can order blood tests, including doctors and some dietitians, can order the MRT test.

The MRT test assesses 120 common foods and 30 chemicals. It might grow to include more foods and chemicals—but adding an item will cost at least $30,000 on the development side, says Patenaude, so growth will be slow. If you’re looking to get tested, you can search the database on to find a dietitian licensed to treat sensitivities.

However, some health professionals have doubts about the accuracy of food sensitivity testing. “There is no validated test for food sensitivities,” says Julie Kuriakose, M.D., founder of Hudson Allergy in New York City. “By validated, I mean the test should have documented evidence that provides a high degree of assurance that a specific test will consistently produce a result. The tests can yield false negatives and false positives.”

If you decide to get tested, Patenaude suggests doing so through a certified LEAP therapist (CLT), as anyone with this credential has gone through advanced training on managing adverse food reactions and sensitivities. LEAP is an acronym for Lifestyle, Eating, and Performance, a nutrition therapy that involves eating a restricted diet sans any foods the MRT test shows you’re sensitive to. “[Other professionals] will not understand the diet protocol based on the results,” says Patenaude.

If you don’t want to get tested, you can try a simpler, much slower road. “Food diaries are useful to narrow a list of offending foods,” says Sezelle Gereau M.D., an integrative otolaryngologist at the Blum Center for Health in Rye Brook, New York. “The best and gold standard way to determine if one has a food allergy or sensitivity is to eliminate the foods strictly for three to six weeks and then reintroduce them in small amounts, one by one over a series of days and observe for reactivity.”

How to Treat Food Sensitivities

Because food sensitivities develop slowly over time, it also takes time for them to resolve. And not all of them do resolve. With nutrition therapy based on the MRT test, dietitians help patients with food sensitivities lose their defenses to certain sensitivities. “Think of the immune system as the bouncer at a swanky night club,” says Whitcomb. “Overexposure to a food or chemical can cause the bouncer to think that a food or food chemical is no longer safe, which is what causes the symptoms.”

Using the LEAP protocol, a dietitian will create an elimination diet based on your test results. You’ll start with a small number of foods, then add new foods slowly to make sure you don’t react to foods for which you didn’t get tested. Such elimination diets are shown to be helpful with conditions like Irritable Bowel Syndrome (IBS), found a review study in the Journal of the American Dietetic Association.

Several months down the road, you’ll be able to reintroduce foods you test sensitive to back into your diet. If you have a reaction, you might need to avoid the food for several more months—or much longer. “The immune system has memory, and each white blood cell has a different span of memory,” says Whitcomb. “Depending on the cell or cells that are reacting, you might be able to get one food back in a few months, a few years, or never.”  Whitcomb, for example, tested sensitive to wheat, chocolate, and peanuts. By avoiding those foods for a year, he was able to get them all back. But his sensitivity to soy and chicken remained unchanged. “With chronic sensitivities, specific types of cells called lymphocytes get involved that are long-living cells and can cause sensitivities that can last for years,” explains Pasula.

While you may outgrow a food allergy, you won’t outgrow a food sensitivity. You might, however, regain tolerance to some of the foods you’re sensitive to—meaning you can have some, but you run the risk of having symptoms when eating the food if you overdo it.