What Is the Risk of HIV from Oral Sex?

After more than 35 years of scientific research, the question of whether you can get HIV from oral sex remains confusing.

If asking whether a person can get HIV (human immunodeficiency virus) from oral sex, the honest answer would have to be that it's possible 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.

This article will discuss the risk factors for getting HIV from oral sex and ways to minimize risk.

Theoretical vs. 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. The risk of infection by oral sex is actually extremely low. Not zero, but close to it.

In fact, according to a study from the University of California at San Francisco's Centers for AIDS Prevention Studies, the probability of HIV infection through unprotected oral sex was statistically zero, although the researchers went so far as to add that "we cannot rule out the possibility that the probability of infection is indeed greater than zero."

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 Exposure 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 noninfected person is either performing or receiving oral sex.

However, numbers can change once you factor in specific sexual behaviors. Among them:

• Receptive fellatio, meaning that the noninfected person is performing oral sex on a male partner with HIV, is considered exceptionally low risk. Among men who have sex with men (MSM), the per-act risk hovers at around 0.04%.
• Insertive fellatio (mouth-to-penis contact) is even less likely given that the enzymes in saliva can neutralize the HIV viral particles.
• Cunnilingus (mouth-to-female genitalia contact) has also proven to be a highly unlikely route.
• Anilingus (mouth-to-anus contact) is also regarded as being of negligible risk, particularly for the receptive 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 of 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, including:

• 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 (STIs), like syphilis and gonorrhea, can be asymptomatic. 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 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.

How 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, take your HIV medicine as prescribed. If your viral load remains undetectable, you have effectively no risk of sexually transmitting HIV to HIV-negative partners.
• If you are HIV-negative, you can ask your healthcare provider to prescribe HIV pre-exposure prophylaxis (PrEP)—a type of therapy (either in the form of a daily pill or an injection every two months) that can reduce your risk of infection by more than 90%.
• Regular HIV screening is recommended for persons at high risk of infection, including MSM, injecting drug users, and persons with multiple sex partners. Periodic STI 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.