Is it safe to lip kiss with an unknown person such as prostitutes?
there is a possibility of herpes and syphilis, as well as mono, and if there are open wounded areas in your mouth ( this includes tiny nicks from flossing and brushing, you might not be able to see these!!!) possibly HIV. Be very careful, that's a pretty high risk activity!
The only way to stop STD is practice safe sex. What intimate act has a higher risk for contracting STD depends on one's rational judgment. Cautious is fine, but paranoid is not. Of course, in real life, between consenting adults, stupid decisions will always be made.
Just my 2 cents.