Autism really could be triggered by food allergies, according to new research.
A study of almost 200,000 children found those with the learning disability were more than two and a half times as likely to suffer a food intolerance.
The discovery adds to a growing body of evidence suggesting a disfunctioning immune system dysfunction raises the risk of autism spectrum disorder (ASD).
Corresponding author Professor Wei Bao, an epidemiologist at the University of Iowa, said: “It is possible the immunologic disruptions may have processes beginning early in life, which then influence brain development and social functioning, leading to the development of ASD.”
The study analysed health information gathered by the National Health Interview Survey (NHIS), an annual survey of American households conducted by the US Centers for Disease Control and Prevention.
The children were aged three to 17 and the data was obtained between 1997 and 2016.
It found 11.25 per cent of children reportedly diagnosed with ASD have a food allergy, much more than the 4.25 per cent who are not diagnosed with ASD and have a food allergy.
The finding was observational so Prof Bao’s team could not establish an intolerance the causes autism.
But previous studies have suggested possible links including alterations in gut bacteria and increased production of antibodies and immune system overreactions.
These can lead to impaired brain function and neurodevelopmental abnormalities.
Prof Bao, whose research is published in JAMA Network Open, says these connections warrant further investigation.
He said: “We don’t know which comes first, food allergy or ASD.”
He adding a further study following children over many years since birth would be needed to establish this.
Earlier research on the association of allergic conditions with ASD have focused mainly on respiratory and skin allergy, such as asthma and eczema, which has been inconsistent and inconclusive.
The latest study found 18.73 per cent of children with ASD suffered from respiratory allergies, while 12.08 per cent of children without it had them.
Meanwhile, 16.81 per cent of children with ASD had skin allergies, well above the 9.84 per cent of children who are not autistic.
Prof Bao said: “This indicates there could be a shared mechanism linking different types of allergic conditions to ASD.”
He concluded: “In a nationally representative sample of US children, we found a significant and positive association of food allergy, respiratory allergy, and skin allergy with ASD.
“The association persisted after adjustment for demographic and socioeconomic variables and other types of allergic conditions.
“In addition, the association between food allergy and ASD was consistent and significant in all age, sex, and racial/ethnic subgroups.
“Further investigation is warranted to elucidate the causality and underlying mechanisms.”
Almost one in 12 young children suffer from a food allergy in the UK and they are becoming increasingly common.
Autism has been suspected of being linked to such an intolerance for more than 20 years.
A study two decades ago found a large proportion of autistic children, particularly those with late onset autism, responded well when fed a diet low in wheat, milk and other products linked to allergies.
But experts say diet is unlikely to be a cure.
Autism is much more common than many people think.
According to the National Autistic Society, there are around 700,000 people on the autism spectrum in the UK – more than one in 100.
If you include their families, it affects the lives 2.8 million people.
Possible causes are genetic, viral or metabolic, with triggers including German measles.
It is also linked to epilepsy and associations between difficult labour and ASD have been put forward too.
While autism is not a condition with a cure, the right support at the right time can make an enormous difference to outcomes and the challenges people on the spectrum have negotiating a world geared for neurotypical people.
A third of children on the autism spectrum say the worst thing about it is being picked on at school. The National Autistic Society campaigns for support in schools not to be removed with the current cuts facing schools, as well as more support from adolescents entering the working world. Unemployment statistics for people on the spectrum still reflects the work that neurotypical people need to do to understand the world through the eyes of as many as 1 in 45 people on the spectrum.