[Question #4656] Syphilis from kissing

29 months ago
1 week ago had encounter with female CSW. Open mouth kissing for 10 minutes and handjob. No visible sores. CSW told me she would have sex without protection for extra money. 3 days later developed what appears to be cold sore on lower lip (have had cold sores for many years). Tried to Avoid kissing wife this week, but may have pecked her on the lips. Few questions: 1) I have read conflicting statements one this forum about the risks of syphilis from kissing – most responses say no risk, but some responses say rare level of risk. Do I have risk of developing syphilis from this encounter? 2) Could the blister on my lip be from syphilis? I have read conflicting reports about time until first appearance of chancre – most say 10 days, but some say 3 days. 3) I had a syphilis test today on day 7 that was negative. Does this mean the blister is not from syphilis?  I have read on this forum that once you have an active chancre, the blood test would be positive. Thanks for your help
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
29 months ago
Welcome to the forum and thanks for your question. It arrived just as I was logging in; most users shouldn't expect nearly real-time replies!

Syphilis is rare in CSWs in the US (and western Europe), so the chance your partner was infected is very low. And as you discovered in some of your own research, syphils is rarley transmnitted by kissing.

If this looks and feels pretty much like your past oral herpes (cold sore) outbreaks, that's almost certainly that's what it was, especially if it's in a location typical for your previous outbreaks. Syphilitic chancres are quite different; among other things, they don't have a blister-like appearance. You can google both to see typical photos of both conditions. Equally important, a chance cannot appear sooner than 7-10 days (and usually not until 2-3 weeks) after exposure. To your specific questions:

1) Although kissing is a potential route of transmission, and is always listed in educational materials as a possible way to catch it, this is very rare. In my 40+ years in the STD business, I don't think I've ever seen a case of syphilis that appeared to have been acquired by kissing. There is no realistic risk you acquired syphilis from the exposure described.

2) See above. I've never heard of chancres appearing as soon as 3 days; it simply isn't true, as far as anyone knows.

3) Onset after only 3 days is the best evidence it isn't a chancre. And as noted above, if it looks like a typical cold sore, and in the same location as usual, that's also strong evidence against syphilis. But it takes 3-6 weeks for the syphilis blood tests to become positive, so the negative blood test result doesn't mean anything one way or the other. It's true that blood tests are often positive in the presence of chancres, but that's because chancres don't usually appear before 2-3 weeks.

Bottom lines: Definitely not syphilis; probably just another oral herpes recurrence.

I hope this information is helpful. Let me know if anything isn't clear.

HHH, MD
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29 months ago
Very helpful.  Thank you for the quick response and your wonderful service
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
29 months ago
Thanks for the thanks. I'm glad to have helped.---