Is Eating Ass Safe? Infections, STIs, and Tips

Oral-anal contact, commonly called rimming or analingus, carries real infection risks because it creates a direct pathway between one person’s mouth and another person’s rectal and perianal skin. Bacteria, viruses, and parasites that live in the gut or on rectal tissue can transfer to the mouth and vice versa. That said, millions of people engage in this practice, and the risks are manageable with the right combination of barrier use, vaccination, hygiene, and regular screening. The honest picture is more nuanced than either “perfectly safe” or “always dangerous.”

What Can Actually Be Transmitted

The core concern is fecal-oral transmission. Even when the area looks and smells clean, microscopic amounts of fecal matter carry pathogens. Bacteria like Neisseria gonorrhoeae, Chlamydia trachomatis, and Treponema pallidum (the organism that causes syphilis) can all inhabit rectal tissue, and oral-anal contact provides a route for these organisms to reach the throat or mouth of the giving partner. Rectal gonorrhea and chlamydia are common among people who have receptive anal contact, and a large proportion of those infections produce no symptoms at all, meaning an infected partner may not know they are carrying anything.

Viruses add another layer. Hepatitis A and B can both be transmitted through oral-anal contact.¹ Hepatitis A is shed in stool and is classically considered a foodborne illness, but sexual transmission through fecal-oral routes has driven outbreaks, particularly among men who have sex with men. A study in Romania documented 191 hospitalized hepatitis A cases in a single year across two centers, with more than half among MSM, all of whom were unvaccinated.² Human papillomavirus (HPV) is another concern. Oral HPV infections have been linked to a history of genital warts in either partner, and oral-anal contact is one plausible route for anal HPV strains to reach the mouth.³ Herpes simplex virus, both type 1 and type 2, can also spread between oral and anal sites through direct skin-to-skin and mucosa-to-mucosa contact.

Parasites round out the list. Amebiasis and giardiasis are the two parasitic diseases most commonly transmitted through sexual contact that involves fecal-oral exposure.⁴ While these parasites are more commonly picked up through contaminated water or food, oral-anal sex is a well-documented route. Giardia in particular has been increasingly recognized as a sexually transmitted infection over the past few decades, and researchers have suggested it may be underdiagnosed in that context.⁵ Symptoms of giardia include prolonged diarrhea, bloating, and cramping, but some people carry the parasite with no symptoms at all.

The Problem With Silent Rectal Infections

One of the trickiest things about oral-anal transmission risk is that many rectal infections are completely asymptomatic. A person can have chlamydia or gonorrhea in the rectum, feel perfectly fine, and unknowingly pass it along through oral-anal contact. This is not a rare scenario. In one large screening study, roughly 86% of rectal chlamydia infections and about 67% of rectal gonorrhea infections were found in people whose standard genital test came back negative.⁶ In other words, if you only test the urine or genitals, you miss most rectal infections entirely.

This matters because when infectious proctitis (inflammation of the rectal lining caused by an STI) does become symptomatic, it can involve rectal pain, discharge, bleeding, and urgency. The most common culprits are gonorrhea, chlamydia, herpes, and syphilis.⁷ But many people never reach that stage. The infection sits quietly and remains transmissible, which is why routine screening that includes rectal swabs is so important for anyone having anal sexual contact of any kind.

How Syphilis Fits In

Syphilis deserves special attention because it is surging in many parts of the world, and the biology supporting anal transmission is becoming clearer. Researchers have detected Treponema pallidum, the bacterium responsible for syphilis, at both oral and anal sites in people with secondary syphilis. That finding provides biological plausibility for oral-anal sex as a route of syphilis transmission, beyond the more commonly discussed genital and oral-genital routes.⁸ Primary syphilis can produce a painless sore (called a chancre) at the site of infection, including in and around the anus, where it may go unnoticed. Secondary syphilis produces rashes and mucosal patches that are highly infectious. If either partner has active syphilis, oral-anal contact is a realistic transmission route.

Using Dental Dams and Other Barriers

The most straightforward way to reduce risk during oral-anal contact is to place a barrier between the mouth and the anus. Dental dams, thin sheets of latex or polyurethane, are designed for exactly this purpose and can help prevent the spread of STIs during oral-anal sex.⁹ You can also make a makeshift barrier by cutting a condom lengthwise and laying it flat. The barrier blocks direct mucous-membrane-to-mucous-membrane contact, which is the primary route for bacteria, viruses, and parasites.

In practice, dental dam usage is low. Many people find them awkward, unfamiliar, or hard to find at a store. That is worth acknowledging honestly. If you do use one, keep it in place throughout the activity, use only one side against the skin, and do not flip it over. Use a new one if you switch partners or activities. Flavored varieties exist and may make the experience more appealing. Even imperfect barrier use reduces risk compared to no barrier at all.

What Hygiene Actually Helps, and What Backfires

Washing the anal area with mild soap and warm water before oral-anal contact is a common-sense step that removes surface bacteria and reduces, but does not eliminate, the risk of pathogen transfer. Some people go further and use rectal douching or enemas beforehand, assuming that a “cleaner” rectum is a safer rectum. The evidence suggests this is counterproductive from an infection standpoint.

Frequent rectal douching has been associated with higher rates of rectal STIs, not lower ones. A study of men on HIV pre-exposure prophylaxis found that those who douched weekly or more had roughly 3.5 to 4 times the odds of having a rectal gonorrhea or chlamydia infection compared to those who did not douche, after controlling for other risk factors.¹⁰ A systematic review and meta-analysis echoed this concern, noting that douching may damage the delicate rectal lining and make it more vulnerable to infection.¹¹ The rectal mucosa is thin and easily irritated. Stripping away the natural mucus layer that protects it may actually open the door wider for pathogens. External washing is sensible; internal flushing before sexual activity may do more harm than good.

A related concern involves lubricants, which are more relevant to anal intercourse but sometimes used during oral-anal contact as well. One study found that people who consistently used lubricant during receptive anal intercourse had roughly three times the odds of testing positive for a rectal STI compared to inconsistent users.¹² The mechanism is not fully clear. Some researchers suspect certain lubricant ingredients may disrupt the mucosal barrier or the local microbial environment. This does not mean you should skip lube during anal intercourse, where tissue trauma from friction carries its own serious risks. It does mean that slathering the area with products before rimming is unlikely to add protection and could theoretically be counterproductive.

Vaccines That Make a Real Difference

If you engage in oral-anal contact with any regularity, two vaccines stand out as particularly relevant. The hepatitis A vaccine is highly effective and widely available. Given that hepatitis A spreads through fecal-oral routes and has caused outbreaks linked to sexual transmission among unvaccinated populations, getting vaccinated is one of the single most impactful things you can do to protect yourself.² The vaccine is given in two doses and provides long-lasting immunity. Hepatitis B vaccination is similarly straightforward and protects against another virus transmissible through oral-anal and sexual contact.

The HPV vaccine is the other big one. It protects against the strains of HPV most likely to cause genital and anal warts as well as the strains most strongly linked to cervical, anal, and oropharyngeal cancers. Because HPV can spread through skin-to-skin contact at anal and oral sites, vaccination before exposure dramatically lowers the risk. In many countries, the HPV vaccine is now recommended for all people through their mid-twenties and is available to older adults who want it. If you were not vaccinated as a teenager, it is worth asking your healthcare provider whether you are still a candidate.

Getting Tested the Right Way

Standard STI screening that only tests urine or genital swabs will miss a huge number of rectal and throat infections. Current clinical guidelines recommend that people who have receptive anal contact get screened at the pharyngeal, urogenital, and anorectal sites.¹³ That means a rectal swab and a throat swab in addition to the usual urine or genital test. The rectal swab is quick and can often be self-collected, which makes it less uncomfortable than many people expect.

If you engage in oral-anal contact, the giving partner’s throat is also at risk. Pharyngeal gonorrhea and chlamydia are often asymptomatic and may clear on their own, but they can persist and be passed to other partners. Asking specifically for multi-site testing is important because many clinics still default to genital-only screening unless you bring it up. A community-based study in Lima found chlamydia prevalence of about 19% at the anal site and roughly 5% at the pharyngeal site among MSM and transgender women, with gonorrhea at about 10% and 7% respectively at those same sites.¹⁴ Those are not small numbers, and they represent infections that standard testing would miss.

Why People Avoid Bringing It Up With Doctors

Here is where the conversation gets uncomfortable in a different way. Many people who engage in oral-anal sex never mention it to a healthcare provider, which means they never get the site-specific screening that would catch asymptomatic infections. Research into why this happens points to stigma as the central barrier. In qualitative studies of men who have sex with men in the United States, participants described multiple layers of stigma around anal sexual practices that actively discouraged them from seeking care. The stigma was experienced directly (from healthcare providers, partners, and social contacts), internalized (producing shame and discomfort), and anticipated (expecting judgment or poor treatment in the future). This led to concealment of sexual behaviors even from doctors, and participants described this concealment as widespread and damaging to their health.¹⁵

This is not a problem limited to any one demographic. Anyone who practices rimming, regardless of gender or sexual orientation, faces the same calculation: is this something I can mention to my doctor? The practical answer is that you should, because the screening you need depends on the activities you engage in. A provider cannot order a rectal swab or recommend a hepatitis A vaccine if they do not know those are relevant. If your current provider makes you feel judged, it may be worth finding one who specializes in sexual health or is explicitly LGBTQ-friendly, though people of all orientations engage in this practice.

Oral Health and Transmission Risk

The state of your mouth matters. Open sores, bleeding gums, recent dental work, and conditions like gingivitis create entry points for pathogens that would otherwise have a harder time crossing intact mucous membranes. If you have an active cold sore (oral herpes), you risk transmitting herpes simplex virus to the anal area, and vice versa. Brushing or flossing shortly before oral-anal contact can cause micro-abrasions in the gums that increase vulnerability. If you want to clean your mouth beforehand, rinsing with water or a gentle mouthwash is a better choice than vigorous brushing.

The same logic applies in reverse. If the receiving partner has hemorrhoids, anal fissures, or any breaks in the perianal skin, the risk of both transmitting and acquiring infections goes up. Inflamed or broken skin sheds more pathogens and also absorbs them more readily.

Practical Risk-Reduction Checklist

No single step eliminates all risk, but combining several measures makes oral-anal contact substantially safer. The strategies that have the strongest evidence or the most logical basis include:

Dental dams: Place a barrier between mouth and anus for every encounter. Use a new one each time.
Vaccination: Get vaccinated for hepatitis A, hepatitis B, and HPV if you have not already.
External washing: The receiving partner should wash the anal area with mild soap and water beforehand. Avoid aggressive internal douching.
Multi-site screening: Request rectal and throat swabs alongside standard genital testing at regular intervals, especially if you have new or multiple partners.
Timing around oral health: Avoid rimming if you have open mouth sores, have just had dental work, or have actively bleeding gums. Do not brush teeth right before.
Open conversation: Talk to partners about recent STI testing and vaccination status. Talk to your healthcare provider about the specific activities you engage in so they can tailor screening.

Who Faces the Highest Risk

Risk is not evenly distributed. People with multiple sexual partners have more exposure opportunities. People with HIV or other conditions that suppress the immune system may be more susceptible to infections and may shed pathogens at higher levels. Unvaccinated individuals face entirely preventable risks from hepatitis A and HPV. And anyone who avoids testing due to stigma or embarrassment carries a higher chance of harboring and spreading an undiagnosed infection.

The giving partner (the person using their mouth) faces the most direct fecal-oral exposure and is at particular risk for hepatitis A, intestinal parasites, and pharyngeal STIs. The receiving partner is more exposed to any oral pathogens the giving partner carries, including herpes simplex virus and, in some cases, oral HPV strains. Both partners benefit from the full spectrum of risk-reduction measures, and both should be screened at the relevant anatomical sites.