Is There A Connection Between Food Allergies And Autism?

It's not uncommon for autistic people of all ages to suffer from gastrointestinal symptoms — like, for instance, abdominal discomfort, diarrhea, constipation, and acid reflux. This often causes parents of autistic children to suspect food allergies, which are rumored to have the ability to "worsen autism symptoms" or even to cause autism. 

Research: Autistic children do have allergies more often?

One study that included a ginormous 199,520 US kids compared the prevalence of allergies among autistic children to the allergy rate in non-autistic children. The findings were interesting:

• A pretty high 11.25 percent of autistic children were found to have food allergies, compared to 4.25 percent of non-autistic children. 
• Autistic children also had a higher rate of respiratory allergies (18.73 percent) compared to non-autistic children (12.08 percent). 
• A total of 16.81 percent of the autistic participants had at least one skin allergy, while the non-autistic group had a much lower rate of 9.84 percent. 
• The differing rates remained statistically significant even after researchers controlled for other factors, like socioeconomic status and ethnicity, indicating that it's really possible there is a link between autism and allergies. 
• It's important to note, though, that while the children labeled autistic in the study were all formally diagnosed, the data regarding allergies was provided through a parent-answered questionnaire — and the allergies weren't necessarily formally diagnosed. That means that not all these children are guaranteed to actually have allergies. 
• The study didn't investigate why the allergy rates different among autistic and non-autistic children, either.

It is, however, absolutely possible for autistic people to suffer from food allergies, just like it is for anyone else.

As for reports that exposure to foods a person is allergic to worsens autism symptoms, well, think of it like this — anyone's behavior would negatively be impacted by symptoms that make them feel bad, and that's perhaps particularly true for people who have trouble verbalizing what they are experiencing, as both young children and some autistic people do. It stands to reason that an autistic child who suffers from food allergies would feel better when they stay away from the allergen in question... and then display behavioral improvements as well, since they're no longer plagued by the nasty symptoms a food allergy can induce. 

How are food allergies diagnosed?

Common food allergy symptoms include swelling of the tongue and throat, trouble swallowing, skin rashes, hives, difficulty breathing, itching, dizziness, pale skin, a weak pulse, and fainting. Fish and shellfish, peanuts and other nuts, eggs, milk, grain, corn, and soy are among the more common allergens — and a person who is allergic would start displaying symptoms, which can include anaphylatic shock that can be life-threatening, shortly after ingesting the offending food, usually within hours but often after minutes. 

After a person develops symptoms that indicate an allergic reaction (something that can develop at any age, though they're more common in infants and children), they or their parents or caregivers will then likely seek medical attention.

Food allergies are best diagnosed by an allergist, who will ask questions about symptoms and the circumstances in which they arose, and then conduct diagnostic testing. This includes:

• Skin prick tests and blood tests for specific allergens — these show whether IgE antibodies, which show up as a result of an allergic reaction, are present. It's important to note that these tests aren't conclusive and a positive skin prick tests doesn't necessarily mean a person will react badly when they eat a certain food. 
• An oral food challenge, in which the person is offered gradually increasing amounts of a certain food, in a strictly controlled environment with medications at the ready, to determine what amounts of the food lead to a reaction. 

However, it would be a mistake for parents of autistic children to assume their children have food allergies or intolerances, or that their children will benefit from specialized diets, by default. There is no solid scientific evidence that autistic children automatically benefit from gluten-free/casein-free diets, for example, and reports that such diets "improve behavior" are based on unscientific, subjective, reports from parents and teachers. Any parent would do well to consult a doctor before placing any child on a special, restrictive diet. This is perhaps especially true for parents of autistic children, since autistic people are already more likely to prefer to eat the same foods all the time — and a special diet could increase the risk of nutritional deficiencies.