I have a friend whose daughter has celiac disease, which destroys the lining in her intestines and is an immune disorder. I've heard of other people who have allergies to various foods, and sometimes to gluten. There is also the possibility that your child is very allergic to some other substance that comes in contact with the food, whether fish or nut oils in processing, or a chemical you use to clean with.
I suggest doing a Google search for gluten-free products and sampling the websites you find. Oats contain a similar protein to gluten which can trigger a response in people sensitive to gluten (either intolerance or allergy). And, having baked something for my friend and her daughter (who had numerous other severe food allergies), I can recommend Gluten-Free Baking Classics by Annalise G. Roberts. It's a wonderful cookbook! http://authenticfoods.com/ Also look up "allergy substitutions" on Google for ways to substitute for the foods he can't eat. :) I love Google and Amazon.