Is food allergy linked to ASD?

Children with autism spectrum disorder (ASD) are more than twice as likely to suffer from a food allergy than children who do not have ASD, a new study suggests.

The study found that, among the participants, 11.25 per cent of children reportedly diagnosed with ASD had a food allergy, significantly higher than the 4.25 per cent of children who were not diagnosed with ASD and had a food allergy.

"It is possible that the immunologic disruptions may have processes beginning early in life, which then influence brain development and social functioning, leading to the development of ASD," said co-author Wei Bao, Assistant Professor at the University of Iowa, in the US.

The finding, published in the journal JAMA Network Open, adds to a growing body of research that suggests immunological dysfunction as a possible risk factor for the development of ASD.

For the study, the researchers analysed the health information of nearly 200,000 children in the US. They were aged between three to 17 and the data were gathered between 1997 and 2016.

The study also found that 18.73 per cent of children with ASD suffered from respiratory allergies, while 12.08 per cent of children without ASD had such allergies; and 16.81 per cent of children with ASD had skin allergies, well above the 9.84 per cent of children without ASD.

"This indicates there could be a shared mechanism linking different types of allergic conditions to ASD," Bao noted.

The researcher said that the study could not determine the causality of this relationship given its observational nature.

But previous studies have suggested possible links -- increased production of antibodies, immune system overreactions causing impaired brain function, neurodevelopmental abnormalities, and alterations in the gut biome, the researchers said.

"We don't know which comes first, food allergy or ASD," said Bao, adding that another longitudinal follow-up study of children since birth would be needed to establish temporality.