I have several posts higher up on the subject. This is coming from an MD. It is safe to get sucked, re HIV. The sucker would have to have bleeding gums and sharp teeth before you would get into trouble.

HOWEVER, If the sucker has oral herpes/cold sores, you can be infected. If he has gonorrhea of the throat, you can get it after a few good thrusts into his mouth, or a few licks of your piss hole (which we professionally refer to as the external urinary meatus). You can get syphillis. You can get hepatitis B. And probably a couple of other nasties. And more likely than not, you can get off and have a fun time.

Sex carries risks. Gay sex carries risks with some interesting twists. But overall, getting sucked tends to be fairly safe. Dr. Danny