I found this article on kissing at Catholic Exchange. As a father of a teenage daughter, I thought it was a very insightful article. The basic idea is this – someone single kissing on the lips, even “closed mouth” kissing, invites more and can lead to a girl losing her virginity through inciting passions. From my perspective, boys are hardwired to want more than just kissing. A girl should protect herself by saving herself, including her kiss, for the man she marries.
Note: I agree with the article that a kiss on the cheek is pretty harmless.
Catholic Eyes Reading 