Some new research shows that allergies are linked to autism. Food allergies can make behavioral symptoms worse, in part because your child may feel uncomfortable and not know how to communicate this effectively.

Autism has also been linked to immune system problems, gastrointestinal issues, and changes to gut microbes, which may be due to sensitivity to certain foods or even food allergies.

What Are Food Allergies?

Anyone who has food allergies struggles with inflammation in the body due to a response from their immune system.

With classic food allergies, the body produces an antibody called immunoglobulin type E, or IgE. When this molecule releases, histamines and other inflammatory molecules trigger the familiar allergy responses like runny eyes and nose, sneezing, coughing, congestion, tiredness, and, in some extreme cases, anaphylaxis or anaphylactic shock.

Anaphylaxis occurs when all of the body systems react to an allergen, such as common food allergens. The inflammation and other symptoms from this reaction can cause a life-threatening condition.

There are also non-IgE allergy responses to particles called allergens. There is no immune system response if the allergen is not present. However, the non-IgE response can be slower than an IgE response, so rather than symptoms like a runny nose and watering eyes, the body may develop pain and discomfort. This is especially true with food allergies.

Symptoms of Food Allergies

Children on the autism spectrum often struggle to communicate. Telling their parents about physical discomfort or allergy symptoms may be difficult or even impossible.

Instead, their behaviors may change. They may become more extreme and avoidant, and they may begin to have meltdowns or bad reactions to meals or certain foods.

If your child has a food allergy, they may display their physical discomfort in these ways:

  • Irritable
  • Hyperactive
  • Falling into repetitive behaviors
  • Difficulty focusing or paying attention
  • Trouble sleeping

Eosinophilic Esophagitis

One type of allergic response is appearing more often among people with autism: eosinophilic esophagitis (EoE). This inflammation causes changes to the esophagus, the part of the throat that leads to the stomach. A type of white blood cell called an eosinophil accumulates in that organ, causing chronic inflammation.

These are symptoms of EoE:

  • Acid reflux that does not respond to medication
  • Trouble swallowing
  • Food getting stuck in the esophagus, called an impaction
  • Nausea and vomiting
  • Abdominal pain
  • Chest pain
  • Refusal to eat due to discomfort or pain
  • Poor appetite
  • Difficulty sleeping
  • Failure to thrive

Some research suggests that the swelling of the esophagus is a combination of both IgE and non-IgE immune responses, which contributes to it becoming a chronic inflammation response.

Are Other Food Issues Common in Children With Autism? 

Food intolerance can cause discomfort and increase behavioral problems in children with autism. Intolerances are not the same as allergies, but they have similar responses and treatments.

While the immune system does not respond to allergens in food, certain foods can still cause digestive discomfort, pain, and distress. Casein and gluten are two commonly reported culprits in children with autism. Autistic children are more likely to struggle with stomach pain, diarrhea, and constipation.

Medical Research Connects Food Allergies & Sensitivities to Autism

Recent medical research has found a link between food allergies and autism in children.

Epidemiologists conducted a study of data spanning 1997 to 2016, leading to an analysis of 199,520 children who were between the ages of 3 and 17 when they participated in research. About 1,868 of the children had been diagnosed on the autism spectrum. They looked for children who had, in a 12-month period, reported eczema, other skin allergies, food or digestive allergies, or respiratory allergies based on physicians’ data.

About 11.25% of children with autism had a reported food allergy, compared to 4.25% of neurotypical children who had a food allergy. Other types of allergies were also reported at higher rates in children with autism compared to their neurotypical peers.

Food sensitivities, rather than allergies, may also be more common in autistic children compared to their peers. People with autism have differences in their gut microbiomes that can cause indigestion and gastrointestinal problems.

Animal models have shown that the gut microbiome can trigger autism-like symptoms. The studies that found this suggest an intimate relationship with gut health, immune system health, and brain function.

The study found that different levels of certain amino acids were present in various body compartments, suggesting a more porous barrier between some systems that could cause inflammation or distress. This difference could also change the gut biome, enhancing digestive issues.

Managing gut health with a combination of treatments, including dietary adjustments, probiotics or supplements, and behavior therapy can all help

Types of Food Allergies Common in Autistic Children

While you can develop an allergy to almost any type of food, there are some types of food allergies that are more common than others. People with autism are most often allergic to the following:

  • Casein, or milk protein
  • Gluten, or wheat protein
  • Soy proteins
  • Corn proteins
  • Egg proteins

Your child may also be allergic to peanuts, shellfish, other types of fish, or tree nuts, although these allergies occur at about the same rate among children with autism as they do among their neurotypical peers.

If you suspect your child has a food allergy, work with your pediatrician to get some tests. Skin prick tests determine whether your child is allergic to certain foods, and blood work can find their level of immune response to the allergen.

A study using a skin prick test (SPT) for egg whites, peanuts, oranges, tuna, walnuts, tomatoes, eggplants, grapes, melons, and dairy was performed on 39 children with autism. Their parents were instructed to eliminate these common allergens from their children’s diets for six months to see if there were any changes in behavior.

The study was inconclusive, as only 3 of the 39 children tested positive as allergic to the foods listed. While the study was inconclusive, food sensitivities or digestive problems may be the actual cause of feeding problems in many autistic children rather than classic food allergies.

Help Your Child With Proper Medical Care

Research is just beginning to show the link between allergies, digestive health, and autism. Some science suggests that food allergies and sensitivities can make autism symptoms more pronounced in children who are on the spectrum.

Working with a behavior therapist can help you understand whether some behaviors, like feeding problems, have a brain-based cause or if they are based instead on physical discomfort, when the child has difficulty communicating. Your child’s pediatrician can help you determine if food allergies are actually present, and a nutritional specialist can design an eating plan that ensures your child is getting appropriate nutrition while accounting for any food allergies.