This article appears in Healthy Living Winter 2018.

Bring up food allergies, and many adults think of things they can’t send to school with their kids. A new study shows they should also be concerned about what foods they’re bringing to work.

Almost half of all food-allergic adults reported that at least one of their allergies materialized in adulthood, according to research presented at the American College of Allergy, Asthma and Immunology Annual Scientific Meeting in October. The study surveyed a nationally representative sample of more than 50,000 adults.

“Food allergies are often seen as a condition that begins in childhood, so the idea that 45 percent of adults with food allergies develop them in adulthood is surprising,” said Northwestern University pediatrician Dr. Ruchi Gupta, lead author of the study. “We also saw that, as with children, the incidence of food allergies in adults is rising across all ethnic groups.”

The most common food allergy among adults is shellfish, affecting an estimated 3.6 percent of U.S. adults. That’s a 44 percent increase from an influential 2004 study. The new data also suggest that adult tree nut allergy prevalence has risen to 1.8 percent from a 2008 estimate of 0.5 percent, an increase of 260 percent.

“Our research also found that, among black, Asian and Hispanic adults, the risk of developing a food allergy to certain foods is higher than for whites, specifically for shellfish and peanuts,” said food allergy researcher Christopher Warren, a doctoral candidate at Northwestern University near Chicago and study co-author.

Allergic in adulthood

Adult-onset allergies likely involve losing immune tolerance to foods that adults have previously been exposed to and eaten without allergic reaction.

“This is in contrast to childhood food allergies, which involve the immune system failing to develop tolerance to these allergenic foods in the first place,” Warren said.

It’s also possible for an adult to develop an allergy to a food they had never previously encountered, “but this is probably not very common given the ubiquity of most common food allergens,” Warren said.

Little is known about how and why allergies develop, making it an area of great research interest, Gupta said. By learning more about food allergies and studying the different demographic and environmental factors that increase risk of development, researchers hope to raise awareness and improve the clinical management of food allergies, Gupta said.

Intolerance or allergy?

Some adults who believe that they have food allergies may actually have intolerances, and vice versa, Gupta said.

“An important difference between a food intolerance and a food allergy is that food-allergic adults may be at risk of potentially fatal anaphylaxis, whereas an adult with a food intolerance is likely to experience less serious, digestive problems and may in fact be able to eat small amounts of the offending food without trouble,” Gupta said.

For this reason, daily management of a food allergy generally requires that greater care be taken to avoid accidental allergen exposure as well as to routinely carry an epinephrine auto-injector in the event of a severe allergic reaction.

“This is why it is so important to see an allergist for a proper diagnosis,” Warren said.

To find an allergist near you, visit acaai.org/locate-an-allergist.