Please read numerous other threads using the search terms "STD transmission risk", "HIV transmission risk", "oral sex", and "fellatio". Not coincidentally, searching "HIV anxiety" will bring up much of the same information. As far as the seeming uncertainty you cite ("zero risk" vs "small but not zero", I'm sure you understand there are few absolutes in biology or medicine. Depending on context of a patient's question, you might tell one person to completely disregard a particular diagnosis as a possibility for a given set of respiratory symtpoms and clinical circumstances, you might leave the door open a bit for another another with similar symptoms.
Here are some bulleted comments on the risk of acquring STD/HIV by receiving fellatio (with apology to the non-professionals for some terms the questioner will understand).
HIV risk: near zero but probably not truly zero; no definitely documented cases.
Chlamydia risk: Same.
Gonorrhea, some risk but lower than for vaginal or anal sex; but no quantitative estimates have been made. Almost always causes obvious symptoms (purulent discharge, dysuria); absence of symptoms within a week is a virtual guarantee of no gonorrhea.
Nonchlamydial nongonococcal urethritis (NGU): It occurs, but zero data exist on per-exposure risk; probably less than 1 in 100. Variable (mostly unknown) causes, but probably no long term consequences and probably no risk to future sex partners. If no symptoms (discharge [usually mucoid or cloudy, not overtly purulent], dysuria), don't worry about it.
Herpes due to HSV-1: Although 50% of the population, and presumably 50% of commercial sex workers, have oral herpes, the large majority are distant childhood infections without recurrent cold sores. In that circustance, asymptomatic viral shedding is uncommon. Unless the partner has an overt oral herpes oubreak--which a partner could easily observe--the risk is very low. But not zero.
Syphilis: Theoretical small risk, primarily in settings with high background rates of syphilis (which does not include heterosexual female sex workers, especially expensive ones [ie, "escorts"]).
Other STDs: No signficant risks I can think of.
Take home message: In the absence of symptoms, neither STD nor HIV testing is indicated on the basis of the encounter you describe.
Good luck-- HHH, MD
PEP would not be warranted by the CDC guidelines and therefore neither would testing.
We have discussed Home Access testing before, and I believe you said you were not aware of exactly what generation test they are using. I found out from Home Access that they use "the updated first generation ELISA". I know a lot of people come to this site and mention buying their test and also inquire about the window period. Would this information lower the approx. 95% accuracy of a 6 week test you sometimes give? Or would the difference for this updated first generation test be negligible?
J
HHH, MD