Youngsters with the condition also have a higher risk of respiratory and skin allergies like eczema and hay fever, researchers said.

The study, led by public health scientists at the University of Iowa in the US, suggested both conditions have a shared origin in a child’s developing immune system.

However, the study, published in the journal of the American Medical Association, Jama Network Open, does not provide any new evidence of such a link and has limitations that mean its other findings require caution.

“It is possible that immunologic disruptions may have processes beginning early in life, which then influence brain development and social functioning, leading to the development of autism spectrum disorders,” said Dr Wei Bao, an assistant professor of epidemiology.

Autism is a condition which changes the way people communicate and experience the world around them, and while some may live independent lives other may have health or learning differences that need support.

The condition was thrust into the spotlight in 1998 when disgraced British doctor Andrew Wakefield warned the measles, mumps and rubella (MMR) triple jab might cause autism, pointing to rising cases worldwide.

This work has since been discredited and withdrawn and experts believe a more likely explanation for rising rates of autism – and allergies – is increasing awareness of the conditions.

Both can present in mild forms that might previously have gone unremarked on, however their causes are not fully understood and are likely to involve a mix of genetic and environmental factors at different times of development.

The latest study looked at data from 200,000 children collected from parents between 1997 and 2016 as part of a routine national health survey in the US.

It found food allergies were 129 per cent more common in children with ASD, and skin and respiratory conditions increased by 50 and 28 per cent respectively.

However the survey, which compiled interviews from a sample of parents about their child’s health each year, does not draw this information directly from their health records.

Parents were instead asked whether their child had a formal diagnosis of autism, or similar developmental condition. They were also asked to self-report whether their child had an allergic reaction to a particular food, skin or respiratory condition in the past 12 months.

This makes the results vulnerable to parents’ biases or what they remember, experts warned.

The findings may show that parents of children with autism are more likely to notice and report minor food and digestive allergies; upsets which parents of children without ASD might ignore.

Dr James Cusack, director of science for the charity Autistica, told The Independent: “It is possible that parents who report one condition are more likely to report another. Such an effect could explain the increase in the reporting of allergies in this study.

“Previous research shows that autism is associated with poorer physical health including asthma, so this finding does make sense in that respect.”

While Dr Bao suggests an immune system origin for both conditions he noted that the study does not look at that and conceded there could be alternative explanations such as genetic or environmental factors.

“Science is never as a conclusive as we want it to be,” Dr Cusack added. “The study adds something valuable in so much as at indicates a link may exist.

“We now need research to do a deeper dive to establish whether a link exists, and then why.”

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