The virus is transmitted between partners when the fluids of one person come into contact with the blood stream of another person. This contact can occur from a cut or broken skin, or through the tissues of the vagina, rectum, foreskin, or the opening of the penis. Oral sex ranks very low on the list of ways HIV can be transmitted. However, the risk of contracting HIV through oral sex is not zero.
Can HIV be transmitted through oral sex (fellatio and cunnilingus)? - NHS
The risk of getting HIV through receiving oral sex that is, a partner's mouth on your genitals is very, very low. We can't say that there's zero risk, because there are a few cases of HIV infection in people who have no other known risk factors for HIV. Also, we can imagine a scenario where an HIV-infected person's mouth is bleeding when he or she is giving oral sex. This could increase the risk of infecting the partner.
Many people find oral sex an intensely pleasurable experience. People use different terms to refer to oral sex including formal terms like fellatio and cunnilingus and slang terms like blow jobs and giving head. Usually oral sex means one person kissing, licking or sucking another person's genitals. Doctors and researchers can't be sure how many people have acquired HIV through oral sex.
The chances of transmitting HIV through oral sex are very low. A person can still take preventive measures, such as by using a condom. HIV spreads through some bodily fluids. The virus can pass through direct contact with fluid or through sharing syringes.