Have you been in touch with the national autistic society,they may be able to advise you of a charity that will pay for you to get the tests done at a private hospital. I most definitely wouldn't bother with shop bought tests,as has been said they are extremely inaccurate. Also your doctor cannot refuse to refer your son for allergy testing if you belive he has allergies. Threaten to report him for discrimination against the disabled...that should scare him into taking you seriously. What makes you think your son may have allergies by the way, does he react in a certain way after certain foods?