The risk of contracting a sexually transmitted infection (STI) when engaging in sexual activity with someone who has an STI depends on a variety of factors, including the type of STI, the type of sexual activity, and the use of protection. While some STIs, such as herpes and human papillomavirus (HPV), can be transmitted through skin-to-skin contact and therefore can be contracted even if a condom is used, other STIs, such as gonorrhea and chlamydia, are more easily prevented with the use of a barrier method like a condom or dental dam.
That being said, it is important to remember that there is always some risk of contracting an STI when engaging in sexual activity with someone who has an STI, even when protection is used. Additionally, some STIs, such as HIV, may not show symptoms right away and can be easily transmitted during sexual activity.
The best way to protect yourself from STIs is to use barrier methods consistently and correctly during all sexual activity, get tested regularly for STIs, and communicate openly with your partner(s) about your sexual health and any concerns you may have.