Can I get HIV from oral sex? For HIV counselors and safer sex educators, that has to be the most frequently asked question of the last two decades. The connection between HIV infection and oral sex has been debated since HIV was discovered. Even the most recent research delivered a not-so-very-definitive conclusion: It depends.

The first thing to remember about oral sex research is that we're talking about putting a penis in a mouth, so it often involves men who have sex with men (even though it's widely practiced by heterosexuals, too). The other kind of oral sex, lips and tongues in vaginas, isn't part of the big research picture despite its popularity among heterosexual men and women. Thus far, researchers don't seem to have any interest in determining how often HIV is transmitted orally via vaginal fluids even though we know HIV is definitely present in those secretions.

In February of 2000, the US Centers for Disease Control, in conjunction with the University of California, San Francisco Options Project, evaluated the risk behaviors of 102 gay and bisexual men recently infected with HIV. The study coordinators utilized a new technology developed by the CDC called Serologic Testing Algorithm for Recent HIV Seroconversions [STARHS], which they claim can more precisely identify recent infections among blood samples. The conclusion? Eight men in the study (7.8%) were infected with HIV via oral sex. These results were presented at the Seventh Conference on Retroviruses and Opportunistic Infections.

Interestingly, during interviews with the researchers, most of the 102 men said they believed oral sex to be safer than other sexual practices, like unprotected vaginal and anal sex. In fact, all oral sex research up to that point supports their assumption. So what happened? When they presented this bit of research, rather arrogantly called the "most definitive study to date," the researchers failed to consider one critical detail: the condition of the men's mouths. The presence of bleeding gums, gum disease, scratches, and ulcers is known to facilitate HIV's ability to enter the bloodstream. But this so-called "definitive" study failed to acknowledge that additional risk. An oversight? Maybe. Nevertheless, it undermines the study's results. No wonder people are so confused about the dangers of oral sex.

When AIDS reporters and experts asked the researcher fielding questions about the study to comment on the conditions of the participants' mouths, he had to admit that at least half of the eight men likely infected through oral sex had gum disease or an oral ulcer. And, oops, researchers failed to mention that seven of the eight men engaged in oral sex that included ejaculation (receiving cum in the mouth). In my opinion, the results of this study are questionable at best. The moral: Beware of researchers promoting definitive studies!

Fast forward to the summer of 2001. A study by researchers from the University of California, San Francisco's Center for AIDS Prevention Studies (CAPS) found that the probability of HIV infection through unprotected receptive oral sex with a man to be statistically estimated at zero. In normal language this means that sucking a man's penis without a condom is a low-risk behavior.

For this study, 198 participants were recruited from anonymous testing and counseling sites in San Francisco. (Does every sex study take place in California?) One hundred percent of the participants identified as gay or bisexual and reported no anal or vaginal sex or injection drug use in the six months prior to entering the study. The participants reported a median of two receptive oral sex partners, and 98% reported unprotected receptive oral sex. Of that group, 89% did not use a condom and 40% swallowed ejaculate (cum).

The participants were screened for HIV infection and also for recent HIV infection using both the standard test for HIV and a test for HIV that is "detuned" to detect only those HIV infections that have occurred within the six months prior to taking the test. Out of the 198 participants, only one HIV infection was reported, and that infection had not been recently acquired and could not be attributed to the period of exclusive oral receptive intercourse. No other HIV infections were detected by the study. Statistically, the study yielded a zero probability of acquiring HIV orally.

That's not the end of the story, of course. The study's lead author, Kimberly Page Shafer, Ph.D., M.P.H., assistant professor of medicine at UCSF, cautioned that the results are based on a relatively small sample, so "we can not rule out the possibility that the probability of infection is indeed greater than zero." Amen, Kimberly.

So there you have it. Two studies, a year and a half apart, with significantly different results. We'd all like to believe in the zero-risk scenario when it comes to oral sex, but you won't find a single credible scientist or researcher who accepts that theory. The most realistic way to view it goes like this: The risk of becoming infected with HIV through unprotected (no condom) oral sex is lower than that of unprotected anal or vaginal sex. Bad oral hygiene (bleeding gums, ulcers, gum disease) and taking ejaculate (cum) in your mouth is a hazardous combination that turns a low-risk sexual activity into high-risk behavior.