A partner of mine made it a practice of using my cum to masturbate himself after I ejaculated. Is this harmful and can it transmit HIV? If we rub our penises together and get each other's pre-cum on each other's penises, is this dangerous?
There have been no reported cases of HIV transmission via the sexual activities you describe, so it is likely very safe. However, other STDs can be transmitted this way, so regular checkups for herpes, syphilis and warts would be a good idea. Learn which STDs can be transmitted via various sexual activities.
To your health,