Hello. A few days back I (straight male) had an encounter with a female. There was no penetrative sex but she did rub my penis against her genitals (vagina) for a brief moment. I do not think she rubbed the tip of my penis against her vagina but rather grinded on the base of it. However, I would regardless know the chances of possible HIV transmission under the assumption that she did rub my tip as well. I do not have any sores or wounds on my penis. Please doctor, can you give me a breakdown of whether such non penetrative unprotected act can result in HIV transmission. Looking forward to your reply. 

Welcome to the Forum  Thanks your your questions and your implied confidence in our service.  I'll be glad to comment.   There is no risk for acquistion of STI from rubbing your penis against a partner's genitals without penetration- for HIV, as well as gonorrhea, chlamydia and trichomonas, if there is no penetration, there is no risk for infection.  This is true even if she rubbed the tip of your penis.---