I had an encounter last night to be part of a sexual interest I've had for a while. I was with a women who was giving oral sex and manual stimulation to a group of other men who then ejaculated on her. She was manually stimulating me and then for a quick second started to out jer mouth on my penjs before I pulled away. I am concerned about my STI risk, including herpes. Could other men's semen that she may have had on ner hand pose a higher risk? The brief encounter with her mouth, does increase my risk?  Is there any preemptive thing I can do?

I have a somewhat mixed response to this situation. On one hand, group sex often involves lots of physical contact with more than one person. If this was a "messy" event in that regard, it is conceivable you are at small risk for STDs transmitted primarily by skin-skin contact (herpes, HPV, syphilis) -- but probably at little or no risk for those transmitted by genital fluids (e.g. gonorrhea, chlamydia, HIV).

On the other hand, even prolonged oral sex can be considered safe sex, with low risk for all STDs, including herpes. Even then, the oral partner would have to be experiencing an outbreak of oral herpes (cold sores), either with or without symptoms:  and even among people with known oral herpes, such outbreaks are quite uncommon, typically no more than once or twice a year. And the very brief oral contact you describe probably is risk free for practical purposes. On top of all that, half of all adults have positive blood tests for HSV1 antibody, usually the result of childhood infection and usually without known herpes outbreaks. Such persons are immune to new infections with HSV1. So you might not be susceptible to HSV1 even if exposed. All in all, I would rate your risk of genital herpes in this situation as well under one chance in many million, i.e. nearly zero. In any case, there is no preventing HSV from taking hold after exposure. (Research in animals shows that anti-herpes drug must be given before inoculation with HSV in order to prevent herpes. When drug is administered even a few minutes after exposure, it doesn't prevent infection.)

So there is no significant risk of genital herpes in this situation. As for other STDs, I wouldn't be worried at all. There's no way to say the risk is truly zero, but if you have no symptoms in the next few days, I really wouldn't be worried about any STD. However, if you are at all uncertain about the details of the exposure events, for further reassurance you could consider testing for gonorrhea and chlamydia (urine test, valid after 4-5 days) and blood tests for HIV and syphilis after 6 weeks.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

Thank you for the clear response. Also, apologies for horribly written question. 

Thank you again for your help with this. I did want to clarify that her lips did make contact, which I am not sure that I made that clear. However, if that was understood, that your impression of risk for all the STI's already explained below is still negligible, correct?