Children with autism are more likely to also have a food, respiratory or skin allergy, new research suggests.

What’s not clear from the new study, however, is whether there’s a common cause behind these conditions.

“More research is needed to determine whether there is a causal relation between allergies and autism, or something else causes both conditions,” said senior study author Dr. Wei Bao, an assistant professor at the University of Iowa.

The study was only designed to find an association between these conditions, not a cause-and-effect relationship. But Bao suggested that a problem in the immune system might underlie these conditions.

Dr. Punita Ponda, associate division chief of allergy and immunology at Northwell Health in Great Neck, N.Y., said she’s definitely seen allergies and autism occur together. But, she added, there are only theories so far on why that would be.

One theory is that the gut microbiome — the natural bacteria found in your digestive system — might be altered somehow, and may trigger inflammation that plays a role in these conditions.

Another, as Bao noted, is a possible common problem somewhere in the immune system, said Ponda, who wasn’t involved with the study.

No matter what the cause, autism spectrum disorders can complicate the diagnosis and treatment of allergies, according to Ponda. Children with autism may not be able to effectively communicate how they’re feeling and what symptoms they’re experiencing. Physical exams may be harder to do, and allergy testing can be a challenge when communication skills are limited, she said.

The study was published June 8 in JAMA Network Open.

In an editorial in the same issue of the journal, Dr. Christopher McDougle, from the Lurie Center for Autism at Massachusetts General Hospital, said doctors should check for food allergies before initiating treatments designed to reduce behavior problems.

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