Kissing does not transmit HIV because saliva does not contain HIV. Even if it does contain HIV, the HIV load in saliva is very low and does not cause HIV infection. Moreover, AIDS is a blood-borne disease and is not transmitted through the digestive tract, so a courtesy kiss will not infect you. However, if the kiss is a tongue kiss or a very deep contact exchange of bodily fluids, it is possible to get infected. For example, if both parties have wounds in their mouths and blood is coming out. When both parties kiss on the tongue, the blood of the AIDS patient may enter the wound in the other person’s mouth and cause an AIDS infection. This is a very rare occurrence and should not be a cause for concern.