Current medical status: My son was diagnosed with autism at the age of 3.
Current medical treatment: speech, occupational, and behavioral therapy

Atypical eating behavior occurs in about three-quarters of children with autism. Selectivity is the most common problem. Although eating rituals and food refusal also occur; this does not appear to result in malnutrition. Although certain children with autism also have gastrointestinal (GI) symptoms, there is a lack of published rigorous data to support the theory that autistic children have more or different GI symptoms than usual; studies report conflicting results, and the relationship between GI problems and autism is unclear.


If your son has chronic diarrhea he will need several diagnostic procedures (standard and specific blood tests, copro culture, colonoscopy, etc.) to exclude several possible conditions (intestinal infection, celiac disease, lactose intolerance, etc.).


You may want to consult a podiatrist about your son’s digestive problem.

A podiatrist? Why don't you just come right and say that "I'm not a doctor, I just play one on the internet"?
Websters defintion:
Podiatry (or chiropody) is a branch of medicine devoted to the study, diagnosis and treatment of disorders of the foot, ankle and lower leg.

Yeah, why would you say podiatrist? Do you mean pediatrician?

I think you should probably take your son to a pediatrician specializing in autism, if you can find one in your area. I would also suggest reading up on diets for children with autism. There is a lot of debate/controversy over the link between diet and autism. Some parents swear that changing their child's diet improves their autism symptoms. Some doctors agree, some (highly) disagree. As long as you are still participating in the therapeutic programs as well, I don't see what harm the diet can do. (Please feel free to disagree).

Do your research and talk to doctors (as many as will listen to you), ask them questions. Remember: you are paying them, so don't let your son or your concerns be dismissed. I really hope you find something that can improve your son's symptoms. I wish you the best of luck.