More than 10 percent of adults in the U.S. – over 26 million – are estimated to have food allergy, and almost twice as many people believe they have food allergy but report symptoms that are inconsistent with a true food allergy, according to a new study from Northwestern Medicine and Ann & Robert H. Lurie Children’s Hospital.

The study, based on a nationally representative survey of more than 40,000 adults, was published in JAMA Network Open Jan. 4.

“While we found that one in 10 adults have food allergy, nearly twice as many adults think that they are allergic to foods, while their symptoms may suggest food intolerance or other food related conditions,” said lead author Dr. Ruchi Gupta, professor of pediatrics at Northwestern University Feinberg School of Medicine and a physician at Lurie Children’s.

Food allergy can trigger a life-threatening reaction.

“It is important to see a physician for appropriate testing and diagnosis before completely eliminating foods from the diet,” Gupta said. “If food allergy is confirmed, understanding the management is also critical, including recognizing symptoms of anaphylaxis and how and when to use epinephrine.”

Nearly half of food-allergic adults developed at least one of their food allergies as an adult, the study found.

“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.”

The study data indicate that the most prevalent food allergens among U.S. adults are shellfish (affecting 7.2 million adults), milk (4.7 million), peanut (4.5 million), tree nut (3 million), fin fish (2.2 million), egg (2 million), wheat (2 million), soy (1.5 million) and sesame (.5 million).

“Our data show that shellfish is the top food allergen in adults, that shellfish allergy commonly begins in adulthood, and that this allergy is remarkably common across the lifespan,” Gupta said. “We need more studies to clarify why shellfish allergy appears to be so common and persistent among U.S. adults.”

Gupta is the Mary Ann and J. Milburn Smith Research Professor for a Sr. Scientist in Child Health Research at the Stanley Manne Children’s Research Institute at Lurie Children’s. She also is director of the Science & Outcomes of Allergy & Asthma Research (SOAAR) Program at Feinberg and Lurie Children’s.

Funding for this study came from the National Institute of Allergy and Infectious Disease grant R21AI135702 of the National Institutes of Health, Sean N. Parker Center for Allergy and Asthma Research at Stanford University and other sources.