A new study is shedding light on how widespread peanut allergies are among the United States’ adult population.

Research from The Journal of Allergy and Clinical Immunology shows there are 4.6 million adults around the nation who are allergic to the legume and many — 800,000 of them — developed it in adulthood, CNN reported.

Dr. Ruchi Gupta, the study’s author and director of the Center for Food Allergy and Asthma Research at Northwestern University in Illinois, said that peanut allergies are generally thought to be a pediatric issue, but the study showed that just 15% to 20% of children will outgrow their allergy by the time they become adults. Gupta noted that more adults have peanut allergies than children.

In the survey of more than 40,000 US adults, it was discovered that those who said they developed a peanut allergy in adulthood were drastically less likely to be diagnosed by a doctor as opposed to adults who received a diagnosis as children.

Rather than following up on a negative reaction to peanuts with an allergy test, Gupta said adults typically avoid the food altogether. She said getting diagnosed with a peanut allergy provides confirmation of the allergy and influences the way you live your life.

The study showed that only 1.8% — or 4.6 million — of the 2.9% of US adults who reported having a peanut allergy had a valid peanut allergy.

Adult-onset food allergies are rare, according to the American College of Allergy, Asthma, and Immunology. In 2019, WebMD reported that the rates are increasing and noted that there wasn’t much research on the topic.

“Prevalence studies such as this one are much needed to help us further define the scope of the food allergy epidemic in the U.S.,” Lisa Gable, CEO of Food Allergy Research & Education (FARE) told the website.

Earlier this month, Lisa Bustin, a 54-year-old mother who lives in Clay, New York, told the Today Show about her discovery of a peanut allergy while she took her 13-year-old son, Nathan, home from hockey practice in January.

“I’m not a big peanut eater,” she said. “I almost never do. Just that day they were in the car and I happened to be hungry and I just didn’t think anything of it because I didn’t ever have a peanut allergy.”

The mother wound up passing out behind the wheel and her son took control of the vehicle and steered them to safety. Although the car hit a slow-moving truck, Nathan managed to steer them to safety and dial 911.

Bustin was diagnosed with a peanut allergy and has a prescription for EpiPen. She also keeps medications with her constantly so that “if it ever happens again, I’m all set.”