First, there's absolutely no risk of genital infection. STDs are not trasnmitted by hand genital contact and rarely by genital-genital contact without penetration. And STDs don't travel through the body to unexposed sites -- i.e. the oral event cannot lead to genital infection.

So the only part of this event of potential concern is the fellatio. And that's low risk for all STDs -- much lower risk than vaginal or anal intercourse, for example. Some STDs are more likely than others, namely gonorrhea, herpes, and HPV, but even these are uncommon. Chlamydia can infect the throat, but quite infrequently. Viral hepatitis extremely rarely. Trich doesn't take hold in the oral cavity -- no worries there. NGU due to normal oral bacteria is a potential risk for your partner, but of course not for you. Syphilis can be transmitted by oral-genital exposure, but syphilis currently is very rare in most heterosexual populations in the US. The average risk of HIV transmission, penis to oral if the penile partner has HIV, is roughly 1 in 10,000 -- which is equivalent to giving BJs to HIV infected men once daily for 27 years before transmission might be likely -- and assuming your partner wasn't bi or an injection drug user, the chance he had HIV is under 1 in a thousand, dropping your risk to something like one chance in 10 million. I trust you'll agree that's zero for all practical purposes.

For these reasons, in general STD testing is not recommended after a single exposure of this sort, unless the partner is known to have a particular infection, or if symptoms develop. That said, many people in your situation are more reassured by negative testing than professional opinion, no matter how expert and science-based (as we strive to be on this forum). If you'll sleep better with negative testing, the main test of importance is a throat swab for gonorrhea and chlamydia. (Chlamydia testing actually isn't necessary and most experts would recommend against it, except that gonorrhea testing automatically includes chlamydia.) That test is valid any time more than 3-4 days after exposure, so you can do it pretty much any time you wish. The only other tests you might consider are blood tests for syphilis and HIV, the results of which are conclusive 6 weeks or more after exposure.

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

HHH, MD

The man I engaged in these acts with is a white male, aged 30, and heterosexual, unknown sexual history. 

For those reasons, these comments do not alter my advice above. Does that help clarify things?

That concludes two follow-up comments and replies included with each question and so ends this thread.