Far more people in the United States are allergic to sesame than previously thought, a new study finds.

The research, published Friday in JAMA Network Open, found that more than 1.5 million Americans had a sesame allergy — roughly five times the previous estimate. That includes people who were diagnosed with the allergy by a physician, as well as those who weren't diagnosed, but met the researchers' criteria.

The new research looked at data from 78,851 children and adults in the U.S. and found that sesame allergies are just as likely in adults as they are in children. (The researchers extrapolated from their findings to estimate that the allergy affects more than 1.5 million people.)

Although sesame allergies are not as common as nut, egg or wheat allergies, the new research suggests that the allergic reactions to sesame can be just as dangerous.

Many of the people with a sesame allergy reported experiencing a severe allergic reaction, and one-third reported having had to use an epinephrine auto-injector. That's a sign the person was experiencing anaphylaxis, a life-threatening allergic reaction.

But while most food allergens — peanut, tree nuts, milk, egg, soy, wheat, shellfish and other seafood — are required to be listed on food packaging labels in the U.S., sesame is not.

Food allergy awareness groups have been pushing to get sesame on that list for years. Last fall, the Food and Drug Administration took its first steps toward changing labeling requirements to add sesame as an allergen. The agency asked for data on sesame allergy prevalence, and it's expected the new research will be considered by the FDA.

"It’s extremely difficult to avoid an allergen that isn’t required to be labeled in plain language," said Kenneth Mendez, president and CEO of the nonprofit Allergy and Asthma Foundation of America.

In fact, sesame often goes by different names. A main ingredient in hummus, for example, is tahini, which is sesame paste. Gingelly oil — often found in recipes for Indian cooking — is made from sesame seeds.

And even if consumers are already aware of these particular food items, sesame can also be listed simply as "spice" or "natural flavor" on labels.

"People have to call food manufacturers and ask, 'does this contain sesame?'" Mendez said. It's a question many companies refuse to answer because it's proprietary information, according to the AAFA.

Mendez told NBC News the AAFA has received consumer reports of hidden sesame in tomato sauce, bean dip — even maple syrup.

It's why Stacey Saiontz, of Chappaqua, New York, refuses to allow her 11-year-old son, Jared, to try new foods that she can't prove don't contain sesame.

"There are lots of products that we want to buy but can't because we don't know they are safe enough for our son," Saiontz told NBC News.

"There's lots of times when he desperately wants to eat something like barbecue sauce," she said. "So many products look like they could potentially be safe, but it's unclear whether they are because companies don't have to tell you."

A hotel chef went out of his way to prepare allergen-free meals so Jared Saiontz, 11, could eat safely on a family trip to Israel in Dec. 2018. Courtesy of Stacey Saiontz

Sesame is just one of the many food allergies that Jared has, Saiontz said — a commonality he shares with many others.

Indeed, in people with sesame allergies, "80 percent had multiple food allergies, so they are avoiding many foods — not just sesame," said study co-author Dr. Ruchi Gupta, a professor of pediatrics and medicine at Northwestern Medicine and Ann & Robert H. Lurie Children's Hospital of Chicago.

That can take a toll: "It's that day-to-day impairment in your quality of life stemming from the fact that you're worried about your next bite putting you in the emergency room. It's that anxiety that we're trying to avoid," lead study author Christopher Warren, an epidemiologist at Northwestern University Feinberg School of Medicine, said.

Proper diagnosis is key so patients can safely eat some foods, and avoid foods to which they are truly allergic.

"This is a true public health problem," said Lisa Gable, CEO of Food Allergy Research & Education (FARE), a nonprofit that advocates for food allergy awareness and education.

FARE is supporting federal legislation called the FASTER act, which is aimed in part at boosting funds for research into allergy prevalence and treatment.

"It would also add sesame to the list of major food allergens requiring labeling and disclosure," Gable said, adding that FARE is also pushing for the FDA to make the labeling change as soon as possible.

Other countries already list sesame as an allergen on food labels, including Australia, Canada, the European Union and New Zealand.

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