Hello.
I'm not sure what you're asking. It seems as though you might be under the impression that somehow semen or sperm is harmful if swallowed or if left on your face. In some cases, it most certainly CAN be.
Swallowing semen: it isn't fattening, and it doesn't contain anything harmful to your stomach. HOWEVER, if it contains any pathogens, these might find a place to invade your body when they reach your mouth. For instance, you might have a tiny puncture somewhere in your gums after vigorously brushing your teeth. For this reason, it's not safe to swallow semen.
And your face isn't immune to having a tiny puncture or tear either. Even if you can't see it, there could be a small sore, pimple, etc., which would provide access to your bloodstream.
You need to know more about reducing your risk of infection. I suggest you refer to MedHelp's risk reduction site to learn more about this issue:
http://www.medhelp.org/medical-information/show/1723/Safe-sex-