(CN) – More than 1 in 10 Americans have a food allergy, while twice as many claim they have one when they actually don’t, a new survey published on Friday discovered.

Almost 11 percent of U.S. adults, about 26 million, have some sort of food allergy, with some 12 million estimated to not appear until adulthood, according to research published in the Journal of the American Medical Association.

The survey, conducted for nearly a year, asked 40,443 U.S. adults if they had any food allergies. Of those who said they did; only 48 percent said they received a medical diagnosis for the allergy from a doctor, 38 percent said they had to go to the emergency room due to their allergy and only 25 percent said they had a prescription for EpiPen.

“Nearly twice as many adults think that they are allergic to foods, while their symptoms may suggest food intolerance or other food related conditions,” lead researcher Dr. Ruchi Gupta, pediatrics professor at Northwestern University Feinberg School of Medicine said in a written statement. “It is important to see a physician for appropriate testing and diagnosis before completely eliminating foods from the diet.”

The survey asked respondents to describe their symptoms of their food allergy in order to determine if it was real. Researchers looked for the most common reactions the body takes in response to an allergen: vomiting, chest pain, breathing problems, hives, throat tightening, low blood pressure, fast heartbeat, trouble swallowing, swelling of the mouth or tongue or chest tightening. Other reports such as diarrhea or an itchy sensation was considered not to be an allergy and more likely a food sensitivity.

According to the survey, 48 percent of food-allergic adults said their allergy developed in adulthood. The study found that shellfish was the most common allergen, followed by milk and peanuts.

“We were surprised to find that adult-onset food allergies were so common,” Gupta said. “More research is needed to understand why this is occurring and how we might prevent it.”

Researchers also discovered in the survey that women were more likely to have a food allergy than men, 13.8 percent to 7.5 percent.

The latest data shows that Americans spend about $25 billion a year in treating food allergies.