I had unprotected oral (giving), with a female CSW. Although I know syphilis is rare I'm very worried about it. My partner kissed me on the lips 24/48 hours after. What are the chances I transmitted, if I had it? Dr Google says that it cant be transmitted soon after incubation. 4/5 days later I had a sore throat, no obvious lesions, I know this is early for syphilis but I've seen studies from the 50's saying that symptoms can appear within 4 days. 

My doctor suggested strep infection and gave me Doxcy. Sore throat disappeared 2 days later.

My overall fear is if I could have transmitted anything prior to the antibiotics. My only act were dry kisses, only once on the lips.

Thank you

Cunnilingus -- oral contact with female vaginal/genital area -- is low risk for all STIs. Syphilis is very unlikely, especially since you did not develop an oral sore (chancre) within the next couple of weeks. Sore throat is almost never due to STI; it is much more likely that you had a minor viral infection that had nothing to do with the sexual exposure 4-5 days earlier. Probably the doxycycline made no difference, i.e. your sore throat would have cleared up without it. In any case, taking doxycycline would have aborted syphilis if you had been exposed, so there is no need to test for it. If you would like additional reassurance, you could have a throat swab for gonorrhea; if you do it, you can expect a negative result. In any case, no STIs are transmitted by kissing and certainly not without open mouth kissing, even in the unlikely chance you had been exposed. You need not say anything to your partner and they do not need testing for anything.

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

HHH, MD

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So just to clarify that because there were no sores present I could not have infected them? I only ask because I saw a paper from 2024 about syphilis in saliva. Although they did say it was mainly in secondary syphilis with some detected in primary syphilis but only after a titer of 1:8. 

Also am I right in saying that the sore throat appeared too early for it to be classed as syphilis? The symptoms began 48 hours after oral as the back of my throat was red and inflamed, the 4th/5th day, it began to become painful. 

Finally in terms of kissing I would have had to have ulcerated or well established sore on my lip? Some saliva would have been zero risk?

Thank you for your help

Syphilis is not known to cause sore throat -- and yes 4-5 days is too soon for syphilis symptoms. You caught a cold, which -- unlike syphilis -- is easily transmitted by kissing or any close contact.

The amount of doxycycline you describe is more than enough to abort syphilis, i.e. to prevent infection before it takes hold.

Just to clarify, I was only taking 100mg a day not the 200mg recommended. Your opinion still stands?

Finally and as I said earlier I plan to do a test for reassurance. How long after finishing antibiotics do you recommend? And if, there was the very small chance I was infected would it show regardless of the antibiotics?

That's all I have to ask. Thank you for your help and have a Merry Christmas

Syphilis is readily transmissible in the absence of visible sores, because mucosal infection (e.g. the linings of the genital tract and mouth) can be infected without visible abnormality. However, this does not imply you are at high risk of syphilis in this situation and it doesn't mean you could have infected your partner. Syphilis is not transmissible to a new partner sooner than 2-3 weeks after catching it, even without doxycycline. And with doxycycline, there is zero chance you have syphilis now.