Could there be a link between autism and food allergies? A new study from the University of Iowa suggests one, but researchers are still trying to discover how and why.
The study, published online Friday, found that children with autism spectrum disorder, or ASD, are more than twice as likely to suffer from a food allergy than children who do not have ASD, reports the university's news site, Iowa Now.
Researchers analyzed the health information of nearly 200,000 children between the ages of 3 and 17 collected by the U.S. National Health Interview Survey, an annual Centers for Disease Control and Prevention survey of American households. The data covered 1997 to 2016.
The study found that 11.25 percent of children reportedly diagnosed with ASD have a food allergy, compared with the 4.25 percent of children who are not diagnosed with ASD and have a food allergy.
The findings, researchers said, add to a growing body of research that already suggests immunological problems as a possible risk factor for developing autism.
Because the study is observational, though, researchers couldn't identify a cause-and-effect relationship between food allergies and autism, said Wei Bao, an author of the study and assistant professor of epidemiology at the university.
“We don’t know which comes first, food allergy or ASD,” Bao told Iowa Now.
Previous studies about a possible link between autism and allergies focused mainly on respiratory and skin allergies, and yielded inconclusive results, Bao said.
The Iowa study found 18.73 percent of children with ASD also had respiratory allergies, compared with 12.08 percent of children without ASD who had them. It also found that 16.81 percent of children with ASD had skin allergies, compared with 9.84 percent of children without ASD.
That suggested to researchers some type of mechanical link between the two.
But more study will be needed to understand how allergies and autism, both on the rise, could be connected, pediatric allergist Scott H. Sicherer at the Icahn School of Medicine at Mount Sinai in New York, told the American Journal of Managed Care.
“I wouldn’t want people to misinterpret this to say that a food allergy is causing autism,” nor should children with ASD be routinely screened for food allergies, Sicherer told the Journal.
One issue: Parents of children with autism might report their children have a food allergy, but it's not always possible to know whether it's really an allergy or simply a behavioral preference, Sicherer said.
Still, Thomas Frazier, chief science officer for the advocacy group Autism Speaks, told HealthDay News that parents and physicians need to be aware "of the increased prevalence and ensure that individuals receive appropriate evaluation for allergies with subsequent treatment.
"This is particularly true for very young children and nonverbal or minimally verbal children who may not be able to express to parents or providers the effects of allergies."
Frazier told HealthDay that the findings suggest allergies could be a contributing factor to challenging behaviors, such as irritability and mood shifts, in people with autism.
The study, “Association of Food Allergy and Other Allergic Conditions with Autism Spectrum Disorder in Children,” was published online in the JAMA Network Open.