QUESTION
Last night, a guy edged me for 20 minutes or so by putting lube on his penis and rubbing it between my legs around my anus. I noticed that lube got on my anus and he used this lube to insert his finger into my anus. Soon after, we had anal sex with me as the bottom. I did not see a lot of pre-ejaculate on his penis at any point.

My question is: What are the chances that his pre-ejaculate got mixed in with the lube and then transferred an STD to me via insertion of his finger into my anus? I almost tried to get PEP (post-exposure prophylaxis), but after he inserted his finger and before anal sex, I took a shower and washed the outside area off with soap and hot water, so I thought my risk would be low.

ANSWER
You thought correctly. HIV is very sensitive to air and light. Between the lube, pre-cum, and fingers, the risk of transmission was low. You would be at higher risk if he was HIV positive, inserted his penis into you without a condom, and released his ejaculate inside you.

Pre-cum can transmit other STDs more easily though—like gonorrhea or chlamydia. Those germs can be more readily spread and that’s part of the reason why we recommend men who have receptive anal sex—regardless of condom use—get regular rectal screening tests for chlamydia and gonorrhea. Our studies show that between 5-10% of "bottoms" carry rectal infections and most don’t know it. Much more accurate rectal tests called nucleic acid amplification tests or NAATs that pick up a very small amount of chlamydial or gonoccocal DNA are available in San Francisco public health clinics and increasingly, at private doctor’s offices, to diagnose these rectal infections.

If you continue to be sexually active, it is important that you have routine STD/HIV screenings done. In San Francisco, we recommend that you test for STDs every 3 - 6 months. For more information about STD testing, diagnosis and treatment, you can visit the City Clinic website

To your health,
Dr. K