Summary

• The risk of getting HIV throughoral sex is low, but not non-existent. Infection via receptive oral sex (‘doing it’) is biologically plausible and almost certainly happens occasionally. However the difficulty of gathering evidence means that scientists do not agree on the proportion of sexually-transmitted HIV infections that come from oral sex.
• The most plausible minimum and maximum figures are 0.1% (one infection per 1000 HIV infections) and 5% (one infection per 20).
• The UK’s Health Protection Agency estimates that between 1% and 3% of HIV cases result from oral transmission of the virus.
• Infection is thought to be much less likely if ejaculation into the mouth does not happen; and some evidence suggests that mouth lesions may need to be present.
• There are a couple of case reports of HIV infection from a woman to a man via cunnilingus.
• Infection via insertive oral sex (‘having it done to you’) is probably exceedingly low risk and may be impossible.
• It is not possible to contract HIV infection through kissing.