What are my chances of contracting HIV (or other STD\\s) by touching her anus using my tongue?
The general principle is that transmission of HIV (and some other STDs) may occur if there is exchange of deep body fluid [including mucosal exposure to vaginal secretion, semen, blood, etc]. The buccal mucosa is certainly pertained to mucosa and therefore if there is deep body fluid exposure in the process of oral-anal contact, there is a chance of contracting HIV. Given the fact that the risk of transmission can be different among the various types of exposure or contact, we may understand that the risk of oral-anal contact is much lower than penetrative anal sex. We cannot however assume zero risk of such contact.
