Kids with food allergies are twice as likely to have autism

American kids with food allergies are more than twice as likely to have autism spectrum disorder as kids without, a study of national health data finds. The population-based finding adds to experimental evidence that there may be a connection between false steps or overreactions by the immune system and the neurodevelopmental disorder.

Researchers looked only for an association between allergies and autism spectrum disorder, or ASD, among a total of 199,520 children ages 3 to 17 surveyed from 1997 to 2016 as part of the U.S. National Health Interview Survey. The study was not designed to discover what may be behind the link.

The team found that, out of 1,868 children with autism, 216 had a food allergy — or about 11 percent. By comparison, only about 4 percent of children without autism had a food allergy, the researchers report online June 8 in JAMA Network Open. Kids with autism were also more likely to have respiratory or skin allergies like eczema than kids without autism.

The number of children with autism has more than doubled since 2000, to a prevalence of 16.8 per 1,000 kids. Meanwhile, the number of kids with food allergies rose from 3.4 percent in 1997–1999 to 5.1 percent in 2009–2011.

It is unknown whether developing food allergies may contribute to the development of autism, or vice versa, or if something else is causing both, says study coauthor and epidemiologist Wei Bao of the University of Iowa’s College of Public Health in Iowa City. “The causes of ASD remain unclear,” he says.

Past work in mice and people has pointed to a possible connection between different immune system disorders and autism. There is a higher risk of autism for children with a family history of type 1 diabetes, or with a history on mom’s side of the family of rheumatoid arthritis or celiac disease. Mice that developed a food allergy displayed behaviors characteristic of autism, such as repetitive behaviors and less frequent social interaction, a 2014 study published in Behavioral Brain Research found.

The new finding supports the idea “that different manifestations of immune abnormalities occur in individuals with ASD,” says Christopher McDougle, director of the Lurie Center for Autism at Massachusetts General Hospital in Boston, who wrote a commentary accompanying the study. Food, respiratory and skin allergies are common in the general population, he says, but having these allergies “doesn’t mean your child is going to develop ASD.”