- Genital and oral herpes, which are also transmitted via mouth to genital contact.
- HPV, both cancer causing varieties and the varieties that cause genital warts.
- Syphilis. There is a growing concern about this disease spreading through contact with mouth sores during oral sex.
- Molloscum contagiosum.
STIs that are transmitted by skin-to-skin contact may be difficult to fully prevent by safer sex, since barriers do not necessarily cover all potentially infectious skin. However, practicing safer sex does reduce the risk of skin-to-skin STI transmission from diseases such as herpes and HPV.
In contrast, it is easier to effectively prevent transmission of STIs such as HIV and hepatitis by using condoms and other barriers. These STIs require exposure to infected secretions such as blood, semen, and vaginal fluids for transmission to take place. (Which secretions are infectious varies by disease.) Remember, though, HIV does not spread by casual contact or skin-to-skin contact.