As the risk of transmission through oral sex is estimated to be much lower than for vaginal and anal intercourse in the absence of antiretroviral therapy, it is implausible that the risk of transmission through oral sex is not affected in the same way as other sexual transmission risks when effective treatment suppresses viral load. When HIV is not fully supressed, the risk of HIV transmission through the mouth is certainly smaller than through vaginal or anal intercourse.
If undamaged, the tissues of the mouth and throat are thought to be less susceptible to infection than genital or anal tissues, and an enzyme in saliva also acts to inhibit HIV. Very few cases of transmission through oral sex have been reported amongst gay men despite the continued practice of oral sex often with ejaculation into the mouth by large numbers of men over many years. There are no reliable reports of HIV being transmitted from the mouth to the genitals.
Cases of transmission via cunnilingus are extremely rare, and the reliability of these reports is questionable. There are no reported cases of HIV transmission through kissing. HIV is not able to infect most cells in the mouth. Only one cell type found in the mouth is vulnerable to HIV infection Campo.
The tissue of the mouth and oesophagus is also very thick compared with genital tissues, and fluids stay in contact with it for a very short time because swallowing clears the mouth regularly. The mouth is therefore generally regarded as an unlikely route of HIV transmission. Saliva contains numerous factors that have been found to inhibit HIV and stomach acid is likely to inactivate HIV in the same way as other viruses Malmud.
Kissing, licking or sucking another person's genitals, i. Measurement of the amount of virus in a blood sample, reported as number of HIV RNA copies per milliliter of blood plasma. Receptive anal intercourse refers to the act of being penetrated during anal intercourse. A substance that acts against retroviruses such as HIV. There are several classes of antiretrovirals, which are defined by what step of viral replication they target: nucleoside reverse transcriptase inhibitors; non-nucleoside reverse transcriptase inhibitors; protease inhibitors; entry inhibitors; integrase strand transfer inhibitors.
Case reports of infections through oral sex suggest that factors which may increase the chance of HIV infection through oral sex include:. Brushing the teeth and gums often causes mild abrasions and stimulates bleeding. Safer sex guidelines have sometimes suggested that recent brushing can increase the risk of infection through oral sex. The risk of HIV transmission through vaginal or anal intercourse is effectively zero if a person with HIV is on treatment and has a fully suppressed viral load.
It is logical that if HIV cannot be transmitted through anal or vaginal intercourse when viral load is fully suppressed, the same will apply to oral sex. Cunnilingus is considered very low risk. The very few case reports of HIV transmission are limited to people performing cunnilingus rather than receiving it. In both cases the estimate was zero - no transmissions were reported Baggaley. Collecting reliable data is challenging for several reasons:.
Many reports of oral transmission are in the form of isolated and anecdotal reports, rather than from observational cohorts in which people are regularly questioned about their sexual practices and tested for HIV or other studies with more rigorous follow-up.
A few studies have given higher estimates which are difficult to reconcile with the others. Two authoritative reviews of the evidence of the probability of HIV transmission through oral sex both concluded that, given problems with the available data, it would be inappropriate to provide a precise numerical estimate Baggaley, Patel. If the per-contact risk of oral transmission is 0.
This 0. Many of the studies were carried out before antiretroviral treatment after diagnosis became the norm and so are likely to greatly over-estimate the risk of infection. If viral load is fully suppressed, oral transmission cannot take place. If the majority of sexually active people with HIV are on treatment, the per-contact risk is greatly reduced. Rodger A et al. Sexual activity without condoms and risk of HIV transmission in serodifferent couples when the HIV-positive partner is using suppressive antiretroviral therapy.
JAMA, 2 , You can read more about this study in our news report. Rodger AJ et al. The Lancet , Campo J et al. Oral transmission of HIV — reality or fiction? An update. Oral Diseases, , Malamud D, Wahl SM. The mouth — a gateway or a trap for HIV? AIDS, , Baggaley RF et al. Systematic review of orogenital HIV-1 transmission probabilities.
International Journal of Epidemiology 37 : , Patel P et al. Estimating per-act HIV transmission risk: a systematic review.
Sexual transmission. Primary tabs View active tab Preview. Keith Alcorn. July The risk of getting HIV through oral sex is low, but not non-existent, when a person with HIV does not have fully suppressed viral load. The latest news and research on sexual transmission. Glossary oral Refers to the mouth, for example a medicine taken by mouth. Next review date. This page was last reviewed in July It is due for review in July Related topics. The biology of HIV transmission.