Thank you.

There are no data on the per-transmission risk of syphilis for any single exposure, whether oral, anal, or vaginal sex. Oral undoubtedly is the lowest likelihood of these, and absence of visible lesions on your partner's penis is reassuring (although by no means eliminates all risk). But we can break down your risk into 3 components:  The possibility your partner had early (infectious) syphilis; that if he did, he had an infected penile lesion that you didn't see; and, if both those came to pass, the chance of transmission from a single exposure, I would guess the odds you were infected at well under 1 chance in a thousand. And that's before we even consider the time that has passed and your symptoms.

Most people with new syphilis would have an obvious lesion (the chancre) well before 40 days -- typically 10-20 days, rarely more than 4 weeks. So its absence is reassuring. Could your new canker sore be a syphilitic chancre? In theory, it's possible. There is a reason the names are the similar: "canker" is a variation of "chancre". As medical terminology evolved over the decades, they came to mean different things, but originally any discrete, round or oval sore was referred to as a chancre/canker. (The rare STD chancroid also presents with genital ulcers -- there's the same root word again.) However, syphilitic chancres typically are painless, whereas canker sores (and chancroid) usually are quite painful. If your current sore is typical for your past canker sores, probably that's what you have. And as already noted, it's really too late for onset of a chancre from your exposure almost 6 weeks earlier.

So adding these considerations to the odds discussed above, I would put the chance you caught syphilis at no higher than one in 100,000, maybe as low as one in a million. However, to be completely certain, have a syphilis blood test. Enough time has passed for a conclusive result. You can expect a negative result, but when it comes to a dangerous condition like syphilis, better safe than sorry!

I hope this has helped. Best wishes--   HHH, MD

Thank you. The canker is definitely the same as those I have had over the years and appeared 39 days post exposure. 

I know you have indicated in the past that generally speaking, oral sex is considered safe sex. In light of the higher incidence of syphilis among MSM over the past few years, would you still maintain this advice?  Most sexually active individuals do not use condoms for oral sex because it is seen a generally safer sex but is that advice no longer the case for MSM?

Regardless of how I (or another expert with different views) might characterize the safety of oral sex, you almost certainly did not acquire syphilis from the exposure described above. But as also noted, a test for oral gonorrhea would be a good idea after this sort of exposure.

Many thanks.  That is certainly how I have read your statements on oral sex (low risk for all STDs and zero risk (or nearly zero) for some STDs) -- I certainly did not intend to put words in your mouth and apologize for doing so.  

I did, indeed, go to a clinic to have a syphilis, gonorrhea and chlamydia test done and await the results.  My regular (every 6 month) HIV test was negative.

I guess the disconnect for me has been the current statements by public health authorities describing syphilis outbreaks among MSM, the possible transmission of syphilis through unprotected oral sex and the general acceptance of oral sex being safer sex even without a condom.  I, for one, know no men (or women) gay, bi or heterosexual that use a condom for oral sex (vaginal or penile) while the vast majority of MSM would use condoms for anal sex.  Additionally, while I understand the concern and alarm about the recent rapid increase in new syphilis infections -- which was virtually eradicated in the U.S. a few years ago -- especially among MSM, the numbers even at approximately 15,000 to 20,000 new cases per year appear, at least to me as a lay person, to be still relatively smaller in relation to other STDs (including HIV which has been stable at approximately 50,000 new infections per year in the U.S. for quite some time now).  I'd appreciate your thoughts on the syphilis outbreak among MSM particularly on the role anal vs oral sex have had on that.  If that is not appropriate for this forum, I certainly understand but just felt that since I have you here, I'd try to get clarity from you as an expert so as to better educate myself and shape my own behavior.

I certainly value and appreciate your expertise and thank you for your input on this and other fora.

Glad to hear you have been tested. You can expect negative results. Presumably the gonorrhea and chlamydia tests are being done on a throat swab. It's pointless to do urethral or urine testing if the penis hasn't been exposed. (Oral chlamydia testing actually isn't recommended at all, but that's a topic for a different discussion.)

As for condoms and oral sex, your experience is typical: they are not much used and typically not strongly recommended by public health and STD/HIV prevention experts. This can be viewed as a pragmatic, real world perspective:  the distaste of condoms for oral sex (both behaviorally and literally) is high, and it can be counterproductive to recommend prevention strategies that would be rejected out of hand by many (probably most) sexually active persons. Behavioral science shows that impractical advice leads some people to reject all prevention advice -- the baby goes out with the bathwater. So we tend to place our bets on more practical prevention strategies, like common sense partner selection, condoms for vaginal or anal sex, prompt response to suspicious symptoms, and periodic testing. For these reasons, promoting condoms to MSM for oral sex probably would not make a measurable dent in overall rates of either HIV or syphilis and might be counterproductive, even if a few infections might be prevented in some individual cases.

This doesn't mean that people who want maximum protection shouldn't use condoms for oral sex with high risk partners. Each person should make his or her own decision. But I wouldn't expect wholesale promotion of condoms for oral sex for any population group.

That completes the two follow-up comments and replies for each thread. This thread will be closed.

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