Could the immune system play a role in autism?
It’s a possibility raised by a new study showing that children with autism are more than twice as likely to have food allergies as other children.
The study from the University of Iowa also found that children with autism spectrum disorder (ASD) were also more likely to have other types of allergies.
“Because immunological dysfunction has been postulated as a risk factor for autism, it is imperative to know whether allergic conditions, which are relevant to immunological dysfunction, are associated with autism,” Dr. Wei Bao, an assistant professor in the epidemiology department at the University of Iowa and a study corresponding author, told Healthline. “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.”
What the researchers found
Researchers led by Guifeng Xu, PhD, with the epidemiology department at the University of Iowa, found that 11 percent of children with ASD had food allergies, compared to 4 percent of other children.
In addition, almost 19 percent of children with autism had respiratory allergies while only 12 percent of other children had such allergies.
The skin allergy rate for children with autism was almost 17 percent, compared to the nearly 10 percent rate among children not on the autism spectrum.
“This finding is consistent with other findings relating the immune system to autism, including the maternal immune activation model of autism,” Thomas Frazier, PhD, chief science officer for Autism Speaks, told Healthline.
Allergies are common medical markers for immune dysfunction in children.
This most recent study was based on data from 199,520 children ages 3 to 17 who participated in the National Health Interview Survey between 1997 and 2016.
Rates of food, respiratory, and skin allergies were obtained from questionnaires submitted by parents and guardians.
Frazier said that while the causes of autism remain unknown, factors such as genetics, the environment, and the interaction of the two may play a role. The latter also seems to be the mechanism that triggers allergies.
“Parents and clinical providers should be aware of the increased prevalence and ensure that individuals receive appropriate evaluation for allergies with subsequent treatment,” said Frazier. “This is particularly true for very young children and nonverbal or minimally verbal children who may not be able to express to parents or providers the effects of allergies.”
Concerns about the study
Allergy experts were less impressed with the study methodology and results.
“Although the study authors did find higher incidence of allergies in children with autism versus those without, the findings were not consistent amongst all children, especially in the age group when autism is diagnosed (typically ages 3–11),” said Dr. Purvi Parikh, an allergist/immunologist at New York University Langone Health and a member of the Allergy and Asthma Network.
“Moreover, this is a self-reported study, so we do not know if these patients truly had allergies or not,” Parikh told Healthline. “For example, although they found an association with food allergies and autism among all children, we do not have any confirmation how these children were diagnosed or if in fact they had a true food allergy, as this is one topic that is frequently misdiagnosed.”
Dr. David Stukus, director of quality improvement in the Division of Allergy and Immunology at Nationwide Children’s Hospital and The Ohio State University College of Medicine, called the study “very weak.”
“There are major flaws in this study design, most importantly the lack of verification that any of the parental reported symptoms or diagnoses were accurate, including food allergies and autism,” he told Healthline. “It is widely recognized that food allergies are grossly overestimated by self-report compared with validated measures such as oral food challenges.”
No proven link
The study authors, autism experts, and allergists all agreed on one thing.
They said there is no proven causal link between allergies and autism.
“There have been quite a few [studies] done exploring allergies and autism. However, none have found a strong enough link or causation that we would say allergies are implicated in development of autism disorders or vice-versa,” said Parikh. “We do see many individuals who suffer from both disorders. As well as many individuals with very severe allergies that do not show any signs of autism spectrum disorders.”
Bao said a longitudinal follow-up study beginning at birth could provide more clues about whether food allergies can precede or trigger autism.
Parikh called for studies that involve children with confirmed (rather than self-reported) allergies, including research on the genetic and immunological associations of the two conditions.
“The cause of autism is very poorly understood and any associations may be helpful in shedding light on the disease,” added Parikh. “Moreover, allergic conditions are on the rise in both children and adults, so it is an important association to explore.”