Thank you.

Oral STDs are not rare at all. Gonorrhea of the throat is quite common, from performing fellatio on infected partners. Oral herpes, mostly due to herpes simplex virus type 1 (HSV1), is very common (cold sores, fever blisters) -- not initially acquired by oral sex, but easily transmitted by performing oral sex on partners. Although syphilis usually isn't acquired by oral sex, people infected with syphilis often have active syphilis in the mouth. All these can be transmitted to partners' genitals by fellatio or oral-vaginal contact (cunnilingus). The actual risk tends to be low, and in general receiving fellatio (BJs) is a lot lower risk for STDs than unprotected vaginal or anal sex -- but not zero risk. Fellatio often transmits gonorrhea, especially in men having sex with men (MSM); and around half of all newly acquired genital herpes is due to HSV1 acquired by oral sex. Men receiving BJs also can get nongonococcal urethritis (NGU), although usually this is a minor problem without serious consequences -- probably usually caused by entirely normal bacteria in the mouth and throat.

Few other STDs are acquired by oral sex. There has never been a proved case of HIV transmitted mouth to penis, or by cunnilingus. Chlamydia can infect the throat, but rarely and not easily transmitted to other partners. Trichomonas and Mycoplasma genitalium are two common STDs that rarely infect the oral cavity and therefore are almost never transmitted by oral sex.

For these reasons, it's not at all "odd" that oral sex by a fully clothed partner can transmit STDs. However, the overall risk still is quite low for men with female partners. As already implied, the risk is higher from fellatio by male partners. In general, the risk still is low enough that most experts do not always advise condoms for oral sex (unlike vaginal or anal sex, for which condoms always are advised with non-monogamous partners).

Those comments partly answer the questions in your second thread. Both exposures are low risk:  the large majority of fellatio exposures (receiving BJs) from female partners result in no STD. The chance a male will acquire an oral STD by performing unprotected oral sex on a female partner is very low. But it isn't zero:  there are small risks for oral gonorrhea, herpes, or syphilis. It remains important to choose partners with care, and for all sexually active persons to be tested for common STDs from time to time, even if their only sex is receiving oral sex (fellatio) by either opposite sex or same sex partners. However, straight men usually do not need oral testing, even if they commonly perform oral sex on their female partners.

I hope these comments cover your concerns. Let me know if anything isn't clear.

HHH, MD

In any event, if a woman has an oral STD, how can kissing be safe?

Thank you very much, Doctor.

As for kissing, that's an excellent question. The answers aren't certain. For sure kissing rarely if ever transmits gonorrhea between men and women. Some researchers in Australia believe kissing does transmit gonorrhea between men who have sex with men, but they have no explanation why it's not an issue between males and females. Whatever the reasons, it's really not something you need to be worried about.  But you do need to be aware that you can get penile gonorrhea by receiving oral sex.

This is my last follow-up.

A number of other sources state that a condom does not protect against syphilis. This surprises me and, if true  seems to greatly reduce the value of condom use.

Is this true?

Thank you very much for your kind replies.

That completes the two follow-up comments and replies included with each question and so ends this thread. I hope the discussion has been helpful and you now have a better understanding of oral STDs and STD risks from oral sex. Best wishes and stay safe.