Dr. Ryan, how risky is it to kiss someone who's been diagnosed as HIV positive ? Is saliva that contagious, since it is part of body fluids, or is it not ? Can I get infected by kissing ?
The most important thing to remember is that there is no evidence that saliva transmits HIV; the CDC has not documented transmission occuring through contact with saliva. This makes one's risk for infection when exposed to the saliva of an HIV infected person practically negligible.
The saliva of infected people contains little to no virus, and the virus that is found in saliva is often inactive (not infectious). Studies have found that a protein in saliva inactivates HIV (up to 90% of virus was inactivated in one test tube study) and there is evidence that there are other factors that may contribute to the noninfectious quality of saliva. Also, the mucous membranes of the mouth contain cells that are not as prone to infection as the mucous membranes of the rectum or vagina.
This is why transmission through kissing or receiving oral sex doesn't seem to occur.