Allergies to sesame are more prevalent than previously believed, and consumers need to be better informed, according to new research.

In what has been called the most comprehensive review of sesame allergies to date, a new study found that more than 1.5 million people in the United States, or nearly 0.5% of all adults and children, are allergic to the popular seed. However, unlike ­better-known allergens such as peanuts and milk, there are no government requirements for label warnings on food products that contain sesame.

The researchers, most of whom are affiliated with Northwestern University's Feinberg School of Medicine, say that needs to change.

"Our study shows sesame allergy is prevalent in the U.S. in both adults and children and can cause severe allergic reactions," said lead study author Ruchi S. Gupta, a pediatrics professor with the medical school and director of the Northwestern Center for Food Allergy and Asthma Research. "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."

Sesame in foods is sometimes listed by unfamiliar or unclear names, said co-author Christopher M. Warren, an epidemiologist with the allergy and asthma research center. Some Americans, for example, don't know that sesame is used to make tahini, a main ingredient in hummus, the chickpea spread widely available in supermarkets.

The U.S. Food and Drug Administration is seeking information about sesame allergies before possible regulatory action, such as requiring sesame to be listed on the labels of packaged foods.

Many foods can cause allergic reactions, but federal law requires labeling of only the eight most common allergens. Those are milk, eggs, fish, shellfish, tree nuts, peanuts, wheat and soybeans.

While many food-related allergic reactions are mild, some can be life-threatening.

The new study found that 0.23% of the population have a history of significant sesame allergic reactions. A third of those with sesame allergies reported needing epinephrine, an emergency medication used in the case of severe allergic reactions.

However, the researchers noted that only 0.11% said their allergy had been diagnosed by a physician.

"Clinical confirmation of suspected food allergies is essential to reduce the risk of unnecessary allergen avoidance as well as ensure patients receive essential counseling and prescription of emergency epinephrine," Warren said.

The researchers also found that unlike other allergies that tend to develop early in life and may be outgrown later, sesame allergy appears to affect children and adults to a similar extent.

The findings were published in the Journal of the American Medical Association Network Open.