What is Syphilis? Syphilis is an infection spread by T. pallidum, which is directly transmitted to the syphilitic blisters and mucous membranes on the skin. It is a sexually transmitted infection that can take serious forms if left untreated. The infection is spread through sexual contact with an infected person with syphilitic ulcers (a type of painless ulcer). The infected person does not spread by touching places like door handles. Under this, there may be blisters in the vagina, anus, lips, and mouth. The disease is prone to spread during oral, anal, or vaginal related sexual activity. A painless blister on the surface of the mouth or skin is the first sign of infection. Many times people do not even know about the blisters because there is no pain in these blisters. These blisters are cured on their own, but if left untreated, their bacteria remain in the body. Initial treatment with penicillin can be cured. Syp...