The STIs Anal Sex Can Transmit

Which STIs can actually spread through anal sex?

Anal sex can transmit the same range of infections as vaginal sex, plus a rectal-specific risk most people don't think about: gonorrhea and chlamydia can infect the rectum directly, not just the genitals, and often cause no symptoms there either 1Ref 1Centers for Disease Control and Prevention (2024).About Gonorrhea.Supports that gonorrhea is a bacterial STI that can infect the genitals, rectum, and throat, and is often asymptomatic; used alongside the same facts for chlamydia..

HIV, syphilis, herpes, and HPV can all spread through anal sex too, through the same routes that apply to any other kind of sex — genital fluids for some, skin-to-skin contact for others. What matters practically is naming anal sex specifically when talking with a clinician, since that's what determines which sites actually get included in testing. The same logic runs in reverse for oral sex: the oral sti risk covers what spreads through the mouth and throat instead, a separate but related picture from the rectal one covered here.

The rectal-swab gap: why routine testing might miss it

A standard STI panel built around a urine sample or a genital swab does not test the rectum, so a gonorrhea or chlamydia infection there can go completely undetected unless a rectal swab is specifically collected 1Ref 1Centers for Disease Control and Prevention (2024).About Gonorrhea.Supports that gonorrhea is a bacterial STI that can infect the genitals, rectum, and throat, and is often asymptomatic; used alongside the same facts for chlamydia.. Self-collection kits, including rectal swabs a person can collect themselves rather than have a clinician do it, now make this easier to add to a routine visit 2Ref 2Centers for Disease Control and Prevention (2024).Getting Tested for STIs.Supports that self-collection testing options exist, including for sites like the rectum that a routine genital-only panel would otherwise miss..

The gap exists because a genital-only test is still the default at a lot of visits, not because rectal testing is unavailable. Naming anal sex specifically when discussing testing, rather than assuming a standard panel already covers it, is usually what actually closes the gap — and it's worth doing whether the testing happens in a clinic or through at-home sti kits ordered directly.

What rectal symptoms can mean, and why they're easy to miss

Rectal gonorrhea and chlamydia frequently cause no symptoms at all, which is part of the asymptomatic sti majority that makes routine testing more useful than waiting for a symptom to show up 1Ref 1Centers for Disease Control and Prevention (2024).About Gonorrhea.Supports that gonorrhea is a bacterial STI that can infect the genitals, rectum, and throat, and is often asymptomatic; used alongside the same facts for chlamydia.. When symptoms do appear, they can include rectal pain, discharge, bleeding, or a persistent urge to have a bowel movement that doesn't resolve.

Those symptoms overlap with other proctitis causes that have nothing to do with an STI, which is exactly why a swab, not a guess based on symptoms alone, is what actually identifies the cause. A closer look at rectal symptoms after anal sex covers that differential in more detail for anyone with symptoms right now rather than asking about risk in general.

Because rectal infections so often produce nothing noticeable, the honest baseline assumption for anyone having anal sex regularly is that testing on a schedule, not waiting for a symptom, is what actually catches an infection early. Someone who has never had a symptom and still tests positive is a common, unremarkable outcome, not a sign that something unusual happened.

HPV and the cancer risk anal sex specifically raises

HPV spreads easily through anal sex via skin-to-skin contact, and most infections clear on their own without ever causing a problem. Persistent infection with certain high-risk types is the exception, and it's linked to an estimated 39,300 HPV-associated cancers diagnosed in the U.S. each year, including cancers of the anus 3Ref 3Centers for Disease Control and Prevention (2024).Basic Information about HPV and Cancer.Supports that HPV causes some anal and oropharyngeal cancers among others, and that HPV causes roughly 39,300 cancers per year in the U.S..

That risk is part of why some people with ongoing anal sex exposure, particularly those living with HIV, end up in a conversation about anal cancer screening with a clinician, even though there's no HPV test currently approved specifically for that purpose in men.

HIV and PrEP

HIV can be transmitted through anal sex, and for someone who is HIV-negative and wants an additional layer of protection beyond condoms, PrEP taken consistently reduces the risk of getting HIV from sex by about 99% 4Ref 4Centers for Disease Control and Prevention (2024).Clinical Guidance for PrEP.Supports that PrEP, taken as prescribed, reduces the risk of getting HIV from sex by about 99%, covers oral and injectable PrEP options, and does not protect against other STIs.. It's available as a daily pill or a longer-acting injectable option.

PrEP protects against HIV specifically — it does nothing for gonorrhea, chlamydia, syphilis, HPV, or any other STI covered here, so it works best alongside routine testing rather than in place of it. For someone with a specific recent exposure rather than ongoing risk, a different option, PEP started within 72 hours, is worth knowing about separately.

Condoms and doxy-PEP: how much protection actually helps

Consistent, correct condom use is highly effective against STIs spread through genital fluids, including HIV, gonorrhea, and chlamydia, but offers only partial protection against infections spread by skin-to-skin contact, like herpes, syphilis, and HPV, since a condom doesn't cover every area where those can be present 5Ref 5Centers for Disease Control and Prevention (2024).Condom Use: An Overview.Supports that consistent, correct condom use is highly effective against STIs spread by genital fluids but provides only partial protection against STIs spread by skin-to-skin contact, and describes correct-use steps including lubricant guidance.. That's not a reason to skip condoms during anal sex — they still meaningfully lower risk on both counts — just a reason not to treat them as complete protection against everything.

Added lubrication is part of correct condom use specifically for anal sex, since anal tissue is thinner and tears more easily than vaginal tissue, and reducing that friction lowers exposure to blood or other bodily fluids 5Ref 5Centers for Disease Control and Prevention (2024).Condom Use: An Overview.Supports that consistent, correct condom use is highly effective against STIs spread by genital fluids but provides only partial protection against STIs spread by skin-to-skin contact, and describes correct-use steps including lubricant guidance.. A water- or silicone-based lubricant is the safer pairing with a latex condom — oil-based products can weaken latex and make it more likely to break. This is a detail that gets skipped in a lot of general safer-sex advice written with vaginal sex as the default, and it's worth naming directly rather than assuming the same guidance applies the same way here.

For people who've had a bacterial STI in the past year, doxy-PEP, a dose of the antibiotic doxycycline taken after sex, is a further layer some clinicians now offer to lower the chance of another chlamydia, gonorrhea, or syphilis infection 6Ref 6Bachmann LH, Barbee LA, Chan P, et al. (Centers for Disease Control and Prevention) (2024).CDC Clinical Guidelines on the Use of Doxycycline Postexposure Prophylaxis for Bacterial Sexually Transmitted Infection Prevention, United States, 2024.Supports the 2024 CDC doxy-PEP guideline: recommends offering doxycycline taken after sex to people who had a bacterial STI in the prior 12 months to reduce the chance of a future one.. It doesn't replace testing, condoms, or PrEP; it adds to them for a specific group at higher near-term risk of reinfection. Testing itself is available to everyone regardless of age, including minors, under minor sti consent laws that exist in every state.