I read that the anus is the most susceptible to STDs, especially HIV. Is that true, and if so, why is that?
— Anonymous, from Tumblr
Sarah: Yes, in short because the vagina is designed to have things inserted in it while the anus is not (and no, that doesn’t mean I think people aren’t supposed to fuck it). Basically, the anus is more prone to injury during sex, and thus infection (see below for the specifics). That’s why it’s still important to use condoms even if pregnancy is not a concern. Any virus you might have could get straight into your bloodstream during anal sex, so heed that advice!
Debby: Yes, unprotected anal intercourse does present greater risk for STIs, including HIV, compared to unprotected vaginal intercourse. The primary reason seems to be related to anatomy and physiology. Unlike the vagina (which produces its own lubrication), the anus does not lubricate. The anus is thus more prone to tearing during penetration and those tears (even the many tiny ones that are not visible to the naked eye) create more pathways to the bloodstream for bacteria and viruses to enter. If you’re into anal sex and you’re not sure of your partner’s STI/HIV status, it’s wise to always use condoms and to use lots and lots of water- or silicone-based lubricant to ease penetration. Some people ditch condoms when they have anal sex - either because they don’t want any more friction or because they aren’t worried about pregnancy - and unfortunately that puts people at risk for STIs and HIV. Safer, pleasurable anal sex is possible!