What Is the Risk of HIV from Oral Sex?

Separating Fact from Common Myths and Misconceptions

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After more than 35 years of epidemiological and biomedical research, the question of whether a person can get HIV from oral sex remains confusing to many—and likely more so than it needs to be. So let's start by separating hypothetical arguments from the hard facts and statistics.

If asking "can" a person get HIV from oral sex, the honest answer would be possibly but unlikely.

For the most part, oral sex—either in terms of fellatio (oral-penile), cunnilingus (oral-vaginal), or anilingus (oral-anal)—is not an efficient route of HIV transmission.

However, the word "can" suggests a theoretic possibility that many find difficult to dismiss.

Theoretic vs. Documented Risk of Oral Sex

It's important to understand, however, that there's a difference between a theoretic and documented risk. Documented risk is based on the actual number of cases in which HIV transmission can be directly attributed to an act (or acts) of oral sex. And, when looking through that lens, the risk of HIV infection by oral sex is actually considered very low. Not zero, perhaps, but edging close to it in many cases.

How close? According to a study from the University of California, San Francisco's Centers for AIDS Prevention Studies (CAPS), the probability of HIV infection through unprotected oral sex was statistically estimated as zero, although the researchers went so far as to add that "we can not rule out the possibility that the probability of infection is indeed greater than zero."

Clearly, there are situations which can increase transmission risk, sometimes considerably. But by fully understanding and identifying the factors that can place you at risk, you can make better, more informed decisions about your sexual health, as well as that of your partner.

Assessing Risk from Type of Oral Sex

The likelihood of transmitting HIV through oral sex depends largely on the type of contact involved.

Putting aside all other risk factors for the moment, the potential for infection can vary considerably based on whether the uninfected person is either performing or receiving oral sex.

How much it can vary is not entirely clear although a systematic review by the London School of Hygiene and Tropical Medicine suggests that transmission rates can generally run anywhere from 0% to 1%.

Based purely on the type of sexual contact:

  • HIV transmission by way of receptive fellatio—meaning that an uninfected person is performing oral sex on an HIV-positive man (i.e., "giving a blowjob" or "giving head")—is seen to be possible, albeit statistically low. Among serodiscordant couples (where one partner is HIV-negative and the other is positive), studies suggest that the risk is somewhere between 0% and 1% over the lifetime of the relationship. Meanwhile, among men who have sex with men (MSM), the per-act risk from unprotected receptive oral sex with ejaculation was estimated to be around 0.04%.
  • HIV transmission by way of insertive fellatio ("getting a blowjob" or "getting head") is even less likely and may even be impossible since HIV cannot be passed through exposure to saliva alone. Even with the possibility of blood-tainted saliva, there has yet to be a documented case of infection of this type. Most evidence suggests that low levels of infectious virus and HIV-inactivating agents in saliva act as barriers to transmission.
  • Similarly, while it biologically possible to get HIV through cunnilingus, there have been no documented cases of a woman being infected after having had oral sex performed on her. And while few studies have looked into whether an uninfected person can get HIV after performing oral-vaginal sex, the risk is largely considered to be negligible.
  • Anilingus (or "rimming") is also regarded as being of negligible risk, particularly for the receptive partner. To date, there have been no reported cases of an individual acquiring HIV after rimming an HIV-infected partner.

While these figures suggest that the risk of HIV is low from a population perspective, that shouldn't imply that it is inherently low from an individual perspective.

Clearly, the more risk factors an individual has, the greater the risk of HIV transmission.

It is, therefore, important that you identify your personal vulnerabilities to HIV  in order to make informed choices about you engage in sex with.

What Can Increase the Risk of Oral Sex?

Perhaps the single, greatest factor in assessing the likelihood of HIV infection is the viral load of the infected partner. Simply put, the higher the HIV viral load, the greater the infectivity if that person.  By contrast, sustained viral suppression to undetectable levels correlates to vastly diminished risk, whether you engage in oral, anal or vaginal sex.

There are a number of other factors that can influence the potential for infection:

  • Ejaculation during oral sex is perceived to be riskier than oral sex without ejaculation—although there is no quantifiable evidence that ejaculation can be the sole factor for infection in those who perform receptive fellatio.
  • Cuts, abrasions or sores in a person’s mouth can offer a potential route of transmission. Good oral health should be observed to help minimize bleeding gum disease (gingivitis, periodontitis) and other mouth/throat infections.
  • Certain STDs, like syphilis, can undermine mucosal tissues or cause ulcerative sores. These can often go undiagnosed or are difficult to spot, particularly in the throat, vagina or in the lining of the urethra.
  • Lesions or sores from HIV-related infections like candidiasis or herpes simplex can also diminish mucosal integrity. By implementing antiretroviral therapy, the risk of these other oral infections can be greatly reduced.
  • The level of HIV in vaginal fluids can also increase during menstruation when HIV-bearing cells are shed from the cervix, along with blood and mucosal tissue

Ways to Minimize HIV Transmission Risk

Clearly, the best way to minimize the risk of infection is to practice safer sex, particularly if you have multiple sexual partners or are unsure about the health of your sex partner. These include condoms for men and dental dams for those engaging in either cunnilingus or anilingus.

In addition:

  • If you are HIV-positive, the initiation of antiretroviral therapy, as wells as uninterrupted drug adherence can greatly minimize the risk of passing the virus onto others.
  • Similarly, HIV therapy is recommended for serodiscordant couples to ensure sustained viral suppression of the infected partner. The strategy, known as Treatment as Prevention (TasP), has been shown to reduce sexual transmission risk of all types as much as 96%.
  • Regular HIV screening is recommended for individuals with multiple sexual partners or for persons in high-risk populations, including MSM and injecting drug users.
  • Periodic STD screenings are also recommended for a number of these infections, including gonorrhea and chlamydia, especially for those who are at higher risk for infection. Discuss the appropriate options with your doctor.
  • And finally, communication is tantamount to HIV prevention. In the end, the most harm comes from leaving things unspoken or trying to read the clues about your sexual partner. Learn more about ways to negotiate safer sex or how to disclose your HIV status to someone you're dating. 


Baggaley, R.; White, R.; and Boily, M. "Systematic review of orogenital HIV-1 transmission probabilities." International Journal of Epidemiology. 2008; 37(6):1255-1265.

Page-Shafer, K.; Shiboski, C.; Osmond, D.; et al. "Risk of HIV infection attributable to oral sex among men who have sex with men and in the population of men who have sex with men." AIDS. November 22, 2002; 16(17):2350-2352.

Buchbinder, S.; Vittinghoff, E.; Heagarty, P.; et al. "Sexual Risk, Nitrite Inhalant Use, and Lack of Circumcision Associated With HIV Seroconversion in Men Who Have Sex With Men in the United States." Journal of Acquired Immune Deficiency Syndromes. May 1, 2005; 39(1):82-89.

U.S. Centers for Disease Control and Prevention (CDC). "Vital Signs: HIV Prevention Through Care and Treatment - United States." Morbidity and Mortality Weekly Report (MMWR). December 2, 2011; 60(47):1618-1623.