It is far less common, but possible, to transmit HIV through oral sex, especially if you are a man and you ejaculate into someone else’s mouth. If you have HIV and your partner performs fellatio on you but you do not ejaculate in that person’s mouth, you have an extremely low chance of passing HIV to them. HIV transmission through “fellatio without ejaculation can happen, but it is exceedingly rare,” says Thomas Coates, Ph.D., a professor of medicine and director of the University of California, San Francisco, AIDS Research Institute and the Center for AIDS Prevention Studies. “It’s not ‘no risk,’ but it’s relatively low risk.” When ejaculation occurs during fellatio, the risk of HIV transmission rises; researchers debate what the rate of transmission is but most estimates are between 1 and 10 percent. If you are a woman, having someone perform cunnilingus on you is extremely low risk as well, as long as you are not menstruating.