[Arcenciel]

I think everyone else has done a good job answering, but what I want to add is that if a guy (or a girl) doesn't want to come in contact with the blood, you could always get a dental dam or make one out of a condom. That way, his mouth never has to directly come in contact with your skin.
http://www.pamf.org/teen/sex/std/oral/dentaldam.html <-- info on dental dams
http://std.about.com/od/prevention/h...aldamhowto.htm <-- make your own out of a condom.

Be well!
Jen