Hi there. Thank you for posting your question with Healthcaremagic. I will do my best to help you.
Some people, your son probably included, pass out when they experience severe pain
. This is not of itself all that serious nor a cause for worry. I think I would just let it pass.
If you wanted to you could have a blood test
(CBC) and an ECG taken. Given that your son is autistic however this may cause more upset than its worth quite frankly.
I hope that I have answered your questions fully and been of some help. If you have anymore questions please contact me again anytime.
Dr Andrew Rynne.