A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

What are the risks of heterosexual anal sex?

April 10, 2009

Dear Cecil:

What are the risks of anal sex if the partners are heterosexual and monogamous? Could one contract some disease? And if so, how bad is it?

Cecil replies:

Anal sex, eh? Well, I suppose anything beats another round of Gilmore Girls reruns. But let's get one basic concept on the table right away. While there's no denying anal sex has a certain kinky charm, the rectum was designed as an exit, not an entrance. So yeah, you take some risks.

Since the rectum doesn't produce natural lubrication like the vagina does, anal sex risks tearing the rectal walls or the sphincter — an unpleasant experience under the most favorable circumstances, and one that presents a real chance of potentially lethal peritonitis due to leakage of fecal bacteria into the abdomen. A related and in my opinion pretty stupid risk is when the sex starts in the back and winds up in the front — unless the man rinses himself off first, or swaps the dirty condom for a clean one, he could transfer fecal matter and bacteria into the woman's vagina. (An indication of Norman Mailer's advanced views on the matter is the anal sex scene in An American Dream, in which the protagonist, Rojack, clearly a stand-in for the Mailerian id, repeatedly flips the hapless Ruta back and forth.) A 2004 study by the American Cancer Society showed that women practicing anal sex had more than twice the risk of developing anal cancer, possibly due to increased risk of exposure to the human papilloma virus.

Then we come to the risk of HIV transmission, which can't be ruled out even for those who believe they're in a monogamous relationship. Though research is thin, one study claims unprotected anal sex subjects a heterosexual woman to between 20 and 500 times the risk of HIV infection compared to unprotected regular sex. One problem is that backdoor sex often means lower condom use. A California study of female participants in heterosexual anal sex showed 74 percent never used condoms; a survey of midwestern college students showed condoms were about half as likely to be used during anal sex as vaginal.

Some wonder whether, even with precautions, having penises, dildos, or other objects thrust repeatedly into their anuses will cause permanent damage. Here we rely on studies of male subjects — that's all we've got — and these show mixed results. A 1993 study of 40 anal-receptive gay men found 14 experienced frequent anal incontinence, and tests using a water-filled balloon pulled through the rectum found the anal-receptive men had significantly decreased anal resting pressure. (The lab-coated researcher taking notes while observing this — now there's a scene.) Then again, a 1997 study found that while anal-receptive males had lower resting muscle tone, their peak squeezing strength was the same, with no reports of incontinence.

Many think of anal sex as being a gay male thing, but surveys show anywhere from 20 to 40 percent of heterosexuals have at least tried it, and the percentage may be increasing. Some countries have higher rates — a variety of research suggests Brazil might be the anal sex capital of the world, with possibly half of adults regularly doing it. In Central America, the complete sexual experience is known as los tres platos, or "the three dishes": oral, vaginal, and anal.

While it doesn't rank up there with peritonitis, another risk of heterosexual anal sex is partner disgruntlement. Clearly some women like anal sex, but in a 1994 University of Chicago national survey only 5 percent of women rated it as "somewhat appealing" or "very appealing." A Redbook poll of 26,000 women found 40 percent had done it but only 12 percent liked it. In Puerto Rico — and Latin America as a region seems to be highly butt-sex-friendly — 80 percent of female college students surveyed said anal sex was always or almost always the guy's idea.

Of course, the taboo aspect of anal sex may lead to underreporting among those elements of society that don't write in to the newspapers asking about it. In one study of 1,000 women, researchers found many wouldn't admit to doing it until the second or third interview. Having made allowances for such things, several large-scale studies estimate that maybe 9 or 10 percent of sexually active American women regularly practice anal sex.

One thing to be careful about during anal sex is accessories. Straight Dope readers will recall my lengthy list of foreign bodies removed from the rectums of ER patients. A 2004 paper (illustrated, natch) indicates I need to make some additions, including a can of Playboy brand aerosol deodorant and a Primus camping stove. When will you people learn?

Related Posts with Thumbnails


Baldwin, Janice I. and Baldwin, John D. “Heterosexual Anal Intercourse: An Understudied, High-Risk Sexual Behavior” Archives of Sexual Behavior 29.4 (2000): 357-373.

Chun, A.B. et al. “Anal sphincter structure and function in homosexual males engaging in anoreceptive intercourse.” American Journal of Gastroenterology. 92(3) (1997): 465-468.

Clarke, D.L. et al. “Colorectal Foreign Bodies.” Colorectal Disease 7 (2004): 98-103.

Cohen, C.E. et al. “Sexual trauma associated with fisting and recreational drugs.” Sex Transm Infect 80 (2004): 469–470.

Evans, B.A. et al. “Sexual behaviour in women attending a genitourinary medicine clinic.” Genitourinary Medicine 64 (1988): 43-48.

Halperin, Daniel T. “Heterosexual Anal Intercourse: Prevalence, Cultural Factors, and HIV Infection and other Health Risks, Part 1.” AIDS Patient Care and STDs 13.12 (1999): 717-730.

Miles, A.J.G. et al. “Effect of anoreceptive intercourse on anorectal function.” Journal of the Royal Society of Medicine 86 (1993): 144-147.

Mosher, William D. et al. “Sexual Behavior and Selected Health Measures: Men and Women 15–44 Years of Age, United States, 2002” Centers for Disease Control – Advance Data from Vital and Health Statistics 362 (2005).

Rao, Satish S.C. “Pathophysiology of Adult Fecal Incontinence” Gastroenterology 126 (2004): S14–S22.

Stark, Margaret M. Clinical Forensic Medicine Humana Press, 2005.

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