A sesame allergy may affect more U.S. citizens than once thought, according to a recent study.

Researchers from Northwestern Medicine in Chicago and the Mount Sinai School of Medicine in New York recently conducted a study, published in JAMA Network Open last week, to “provide current estimates of the prevalence, severity, distribution, and clinical characteristics of sesame allergy in the United States,” the study’s authors wrote.

To conduct the research, “Study investigators administered a survey via telephone and web to more than 50,000 U.S. households. The survey asked detailed information about any suspected food allergies, including specific allergic reaction symptoms, details about clinical diagnosis of food allergies as well as demographic information,” according to a press release from Northwestern Medicine. “They obtained responses for a nationally representative sample of approximately 80,000 children and adults.”

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The conclusion? A sesame allergy affects an estimated 1.5 million children and adults — more than once thought, per the study. That’s equivalent to roughly 0.49 percent of the population.

Additionally, “more than 1.1 million (0.34 percent of the population) report either a physician-diagnosed sesame allergy or a history of sesame-allergic reaction symptoms, the study found,” per the press release.

Sesame allergy symptoms can include difficulty breathing, coughing, hives, vomiting and abdominal pain among others.

The study is important because sesame labeling is not currently required by law in the U.S., unlike it is with other allergens such as peanut, milk, and shellfish. This means those who are allergic to sesame are at an increased risk of accidentally ingesting it.

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“Our study shows sesame allergy is prevalent in the U.S. in both adults and children and can cause severe allergic reactions,” Dr. Ruchi Gupta, professor of pediatrics and of medicine at Northwestern University Feinberg School of Medicine, a physician at Ann & Robert H. Lurie Children's Hospital of Chicago, and the study’s lead author, said in a statement.

“It is important to advocate for labeling sesame in packaged food. Sesame is in a lot of foods as hidden ingredients. It is very hard to avoid.”

The study comes after the U.S. Food and Drug Administration (FDA) in October requested more information from medical professionals and researchers on the prevalence of sesame allergies as it advances “a new effort for the consideration of labeling for sesame to help protect people who have sesame allergies.”