Three weeks ago I was diagnosed with secondary syphilis after I went in for testing as I was advised by a casual partner that was tested positive. The sore on my anus that I thought was a hemorrhoid was actually a syphilis chancre. I also have sensitive skin, so my skin often develop hives/red spots all over when it's too hot or nervous (being at the appointment and all), but the doctor believe it might be a faint syphilis rash, so determined that it's secondary rather than primary (I really think it's primary, but I am no doctor). I was prescribed 2 penicillin shots, and was told the syphilis should be clear.
My concern is this. I had made out and had long cuddles (clothed) watching a movie with another person 3 weeks prior to my diagnosis. There was no intercourse or touching of my chancre at the anus area. I have met up with this person again and sees that he has a blister on his upper lip now, which I am not sure if it's a chancre as it had scabbed over and seems flat to the lip. I had advised him of my diagnosis, and to get it checked out, but he seemed to be not worried. He advised that it might have been from the super hot soup he had the week prior and burned his lip. He also said the blister did burst after a week and scabbed over now. I am just extra worried that I might have passed on the syphilis to him after researching online that secondary syphilis rash are contagious. If the doctor was right and I had a faint rash all over, could the blister on his lip be a syphilis chancre just base on making out, cuddle, and regular body contact?