More and more research is pointing toward a link between autism and immune disorders such as asthma and celiac disease. Children and adults with autism show signs of chronic immune system activation and inflammation that affects the brain.
Many researchers think that this chronic inflammation starts before birth, and may be triggered by a mother's infection, allergies, or auto-immune responses. Mothers with celiac disease have a 350% higher risk of having a child with autism than mothers without an autoimmune disorder.
It is also true that the rise in autism has paralleled the rise in food allergies in developed countries. One theory for the reason behind both increasing diagnoses is the hygiene hypothesis - the theory that modern city dwellers lack exposure to bacteria and parasites that help maintain a healthy immune system. Other theories are that exposure to chemicals in our modern environment disrupts normal immune function.
There has been little research on the linkages between food allergies and autism. However, many parents of children on the autism spectrum have placed their children on special allergen-free diets, such as a gluten-free/casein-free diet, or a diet free of nightshade vegetables. While many families have found that these special diets help their children, many others have not. The limited research on GF/CF diets has failed to find any benefit of them at a population level.