Heck personally I don't even know if mites will bite humans as I have had no experience with them myself.

http://www.ball-pythons.net/modules/...warticle&id=46

There is info on external parasites if it's that.

As for the substrate; Are you allergic to coconuts or have you ever had issues with coconut husks? If not then you could probably count that out.

I would suggest that in future handlings you wash your hands right after your handle your snake, this should stop this from happening again, but if you notice your snake laying in it's water dish then it could be mites, in which case you could probably find some mite killer at your local pet store of you could order some online.