More than 10 percent of U.S. adults have food allergies, nearly half of whom developed an allergy in adulthood, according to a new study by Feinberg Prof. Dr. Ruchi Gupta.

The study found 10.8 percent of American adults –– over 26 million people –– have food allergies. It determined another 19 percent have negative reactions to food, but that their symptoms are not consistent with an allergic reaction. Additionally, 48 percent of those with at least one food allergy had developed that allergy as an adult.

Gupta is the director of the Science and Outcomes of Allergy and Asthma Research Team at Northwestern and is an attending clinician at Ann and Robert H. Lurie Children’s Hospital. She is nationally known for her research in food allergy and asthma, according to Feinberg.

The study randomly sampled 40,443 adults from across the nation. Although food allergy in children has been examined in several population-based studies, less is known about food allergy in adults, according to the study. This study is the first to provide comprehensive, nationally representative data on food allergy in adults.

Shellfish was the most common food allergy among adults, with 2.9 percent reporting that food allergy. Milk and shrimp were the next most common, with 1.9 percent each. Gupta stated that a milk allergy is distinct from lactose intolerance, as the former is an immune system reaction while the latter is caused by the lack of a stomach enzyme that allows humans to digest milk.

The study also found that only 24 percent of adults with food allergies had a current epinephrine prescription, which is used to treat severe allergic reactions.

“With true food allergy you can have severe anaphylaxis, which can be life-threatening,” Gupta said. “So it’s really, really important to have a proper management plan, to know what to do, in case you have a life-threatening reaction.”

According to the study, 38.3 percent of adults reported one or more allergy-related emergency room visits in their lifetime.

Gupta said more research was needed to understand allergies that developed in adulthood, suggesting that factors including changes in living conditions, antibody consumption or hormonal changes such as those resulting from pregnancy could be playing a role.

“There’s a lot of different ideas out there that we need better research to understand,” Gupta said.

Christopher M. Warren (Weinberg ’08), a PhD candidate at the University of Southern California who worked with Gupta on the study, said the research team had been granted funding for further allergy studies alongside researchers from the All India Institute of Medical Sciences.

The focus of the research will be on India, Warren said, where citizens experience unusually low levels of allergies but are particularly susceptible to developing allergies when they immigrate to Western countries. Warren thinks that examining this phenomenon will help researchers isolate factors that contribute to the increasing allergy levels in the United States.

“By looking at this systematically, we might be able to identify things that are preventive against allergy that will give us insights into how we can better understand why we’re having this big epidemic,” Warren said.

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