Please NEVER, EVER, EVER take antihistames to help you sleep.
Also, I have had eczema since I was a baby. So does my son. I had to give up my apprenticeship as a Jr Hairdresser because it was so bad.
It's been completely under control since I was a teenager, but I have to keep on top of it.
You really need to talk to a doctor.
There seems to be a connection between ASD and allergies. Have you had allergy tests done? I know what I have to avoid.
None of us are doctors here. The best advice (I hope) I can give is you need to connect with people who are going through the same as you. No-one can empathise more than those folks.
Here's the link again I posted on the AS thread: http://www.psychforums.com/asperger-syndrome/