What Is the Risk of HIV from Oral Sex?

Separating the Facts from Common Misconceptions

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After more than 35 years of epidemiological and biomedical research, the question of whether you can get HIV from oral sex remains confusing to many people. So let's start by separating hypotheticals from the hard facts and statistics.

If asking can a person get HIV from oral sex, the honest answer would have to 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. With that being said, the word "can" suggests a theoretic possibility that many find difficult to dismiss.

Theoretic and Documented Risk

Whenever discussing HIV risk, it is important to differentiate between a theoretic and documented risk. A documented risk is based on the actual number of cases to which HIV can be directly attributed to an act of oral sex. And, when looking through that lens, the risk of infection by oral sex is actually extremely low. Not zero, perhaps, but edging close to it.

In fact, according to a study from the University of California San Francisco's Centers for AIDS Prevention Studie, the probability of HIV infection through unprotected oral sex was statistically 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."

For an individual perspective, there are numerous factors and situations that can increase personal risk, sometimes considerably. By understanding and identifying these factors, you can make better, more informed choices about the sexual health of you and your partner.

Estimating Risk by Oral Sex Type

The likelihood of transmitting HIV through oral sex depends largely on the type of contact involved. Putting aside all other risk factors, the potential for infection can vary based on whether the non-infected person is either performing or receiving oral sex.

Broadly speaking, the risk can run anywhere from zero percent to one percent, according to research from the London School of Hygiene and Tropical Medicine. However, those numbers can change once you factor in specific sexual behaviors.

Among them

  • Receptive fellatio, meaning that the non-infected person is performing oral sex on a male partner with HIV, is considered to be of exceptionally low risk. Among serodiscordant couples (where one partner is HIV-negative and the other is positive), studies suggest that the risk is somewhere around one percent over the lifetime of the relationship. Among men who have sex with men (MSM), the per-act risk hovers at around 0.04%.
  • Insertive fellatio ("getting a blowjob") is even less likely given that the enzymes in saliva can neutralize whatever few viral particles there may be. Even with blood-tainted saliva, there has yet to be a documented case of infection of this type.
  • Cunnilingus has also proven to be a highly unlikely route given that there has never been a documented case of a woman or her partner getting HIV after having received or given oral-vaginal sex.
  • Anilingus ("rimming") is also regarded as being of negligible risk, particularly for the receptive partner. Again, there have been no reported cases of an individual getting 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 you have, the greater the risk of transmission will be

    Additional Risk Factors

    Perhaps the single, greatest factor in determining the likelihood of infection is the viral load of the infected partner. Simply put, the higher the HIV viral load, the greater the infectivity if the person. By contrast, an undetectable viral load corresponds to a near-negligible risk.

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

    • Ejaculation during oral sex is perceived to be riskier than oral sex without ejaculation, although there is no evidence that ejaculation is the sole factor for infection.
    • Cuts, abrasions or sores in a person’s mouth can offer a potential route of transmission. To this end, good dental health should be observed to help minimize bleeding gum disease and other oral infections.
    • Certain sexually transmitted infections, like syphilis and gonorrhea, can cause ulcerative sores or undermine the delicate mucosal tissues of the vagina or anus. Infections like these can often go unnoticed, particularly if they present in the throat, vagina or rectum.
    • Lesions or sores from HIV-related infections like candidiasis or herpes simplex can also compromise the mucosal integrity of the mouth and throat. By taking HIV therapy, the risk of these other and oral infections can be greatly reduced.
    • The concentration of HIV in vaginal fluids can also increase during menstruation as HIV-bearing cells are shed from the cervix. The same can happen if a man gets urethritis, the acute inflammation of which can increase viral shedding even in persons with an otherwise undetectable viral load.

      Ways to Minimize Risk

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

      There are additional strategies that can further reduce risk:

      • If you are HIV-positive, starting and maintaining adherence to antiretroviral therapy can greatly minimize the risk of passing the virus to others. The strategy, known as treatment as prevention (TasP), has been shown to reduce sexual transmission risk among serodiscordant partners by as much as 96 percent.
      • If you are HIV-negative, you can ask your doctor to prescribe HIV pre-exposure prophylaxis (PrEP), a once-daily drug therapy which can reduce your risk of infection by more than 90 percent.
      • Regular HIV screening is recommended for persons at high risk of infection, including MSM, injecting drug users, and persons with multiple sex partners. Periodic STD screenings are also recommended.

      Finally, communication is tantamount to the long-term avoidance of HIV. Whether you are HIV-positive or HIV-negative, the most harm comes from leaving things unspoken. Learn more about ways to negotiate safer sex or how to disclose your HIV status to someone you're dating.

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      Article Sources
      • Baggaley, R.; White, R.; and Boily, M. "Systematic review of orogenital HIV-1 transmission probabilities." International Journal of Epidemiology. 2008; 37(6):1255-1265. DOI: 10.1093/ije/dyn151.
      • 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.
      • Woods, L.; Chahroudi, A.; Chen, H.; et al. "The Oral Mucosa Immune Environment and Oral Transmission of HIV/SIV." Immunol Rev. 2013; 254(1). DOI: 10.1111/imr.12078.