'Surprising' number of food allergies begin in adulthood, study says

New research has found that almost half of people diagnosed with food allergies developed this condition in adulthood, with Hispanic, Asian, and black individuals most at risk.

According to data made available by the Centers for Disease Control and Prevention (CDC), 5.7 percent of children in the United States displayed signs of a food allergy in the past year.

Moreover, a report published earlier this year in The Journal of Allergy and Clinical Immunology stated that almost 4 percent of U.S. adults are diagnosed with food allergies or intolerances.

But at what time in life are allergies most likely to develop? Many studies so far have focused on aspects determining the development of allergies in childhood, such as environmental factors and breast-feeding. Yet are allergies — especially food allergies — primarily relegated to the childhood years?

A new study led by Dr. Ruchi Gupta, director of Science and Outcomes of Allergy and Asthma Research at Northwestern University Feinberg School of Medicine and Ann and Robert H. Lurie Children's Hospital of Chicago — both in Chicago, IL — suggests that almost half of U.S. adults with food allergies developed their condition in adulthood.

The team's findings were presented yesterday at the American College of Allergy, Asthma and Immunology Annual Scientific Meeting, held in Boston, MA.

Many food allergies begin in adulthood

In their study, Dr. Gupta and colleagues considered a representative sample of 53,575 U.S. adults.

Their research revealed that, among adults diagnosed with a food allergy, as many as 45 percent became allergic in adulthood and did not exhibit the same symptoms as children.

"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."

Dr. Ruchi Gupta

Another finding indicated that, worryingly, food allergy trends appear to be on the rise across the board. "We also saw that, as with children, the incidence of food allergies in adults is rising across all ethnic groups," says Dr. Gupta.

Dr. Gupta also points out that the most common type of food allergy seen in adults is to shellfish, which makes up 3.6 percent of cases. This means that the prevalence of shellfish allergy has increased steeply from 2004, when a 2 percent prevalence rate was reported.

As for tree nuts — another widely reported allergy — the researchers found that its prevalence has also increased. Now, 1.8 percent of people with a food allergy report reactions to tree nuts, in contrast with a 2008 study that indicated that "peanut allergy, [tree nut] allergy, or both was reported by 1.4 [percent] of subjects."

Black, Hispanic, Asian people most at risk

Also, different ethnic groups are more vulnerable to allergy onset in adulthood, the researchers noted.

Specifically, black, Hispanic, and Asian individuals are more likely to develop food allergies in adulthood than the white population.

"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," observes study co-author Christopher Warren, a doctoral student.

"For example," he adds, "Asian adults were 2.1 times more likely to report a shellfish allergy than white adults, and Hispanic adults reported a peanut allergy at 2.3 times the frequency of white adults."

Warren also stresses the importance of monitoring any suspicious reactions to food at any age, and promptly reporting them to your doctor.

He urges that "[b]ecause many adults believe food allergies mostly affect children, they may not think to get tested. It is important to see an allergist for testing and diagnosis if you are having a reaction to a food and suspect a food allergy."