The article posted by rainee explains it all, but of course, if
your mate is totally free from HPV genital infection, then you will
most likely be safe as well...
HPV in summary are famous for causing warts (which is an outgrowth
of the epithelial surface on the skin). It is very hard to treat
and once you get it, you will definitely regret... so better avoid
oral sex...
Besides, the vagina provides a suitable niche for several
commensals (bacteria) which makes it their home. If you lick it,
some of it will enter into your mouth and becomes hostile instead
of commensals, because of the difference in the environment.
