Hi,

I just discovered a red flat mark/ lesion on the underside of my penis. It's painless and has just appeared so to be careful I'm going to go for a full STI screening as I had three distinct sexual contacts recently (2 to 4 weeks ago) which involved unprotected oral sex (after being very quiet for months!).

My question is when does a person infected with Syphilis (just in case it is!) actually become 'contagious' to others? If I was infected 3 to 4 weeks ago but had no chancre sore (until today!) does that mean I would not have been infectious to the guy I had sex with 2-3 weeks ago?

I intend disclosing to this individual (as he could also have infected me) but if I could offer some reassurance that he's probably all clear it would be great (as we've been keeping in contact and things have been going really well!)

Thanks for your help!

Hi,

The bacteria that cause syphilis are spread from the sores of an infected person to the mucous membranes of the genital area, the mouth or the anus of a sexual partner. They can also pass through broken skin on other parts of the body. The most common way to get syphilis is to have unprotected sex with someone who has an active infection (a sore or lesion we call a chancre).

Dr. Bob