Sesame is the ninth most common food allergen for kids, and nearly one in three children with a sesame allergy is rushed to the emergency room each year, according to new research.

“This is an allergen that is causing a lot of reactions, and maybe that’s because it is harder to avoid,” said Dr. Ruchi Gupta, lead author of the study and professor of pediatrics at Northwestern University Feinberg School of Medicine and a pediatrician at Lurie Children’s Hospital. “You can’t easily tell if it’s in the food.”

The study also found that nearly 8% of all kids have a food allergy of any kind, and 19 percent of children with allergies need to go to the ER each year. The US CDC has said about 4% to 6% of children have allergies, but those figures are based on older studies.