When I was a teenager I was always amazed that Sis3 would stop crying over a boo boo if I kissed it. I didn't think that it would work the first time I tried it. It did and every time afterward a kiss was all it took to dry up the tears and send her on her merry way (to acquire another boo boo).
Now that I've introduced the concept to Sophia (the boys never went for it) se's gone for it whole heartedly. I realize that the kiss it and make it better approach works with kids because we tell them it works. The first time I tried it on Sophia she immediately stopped crying and went back to playing. That was just a few weeks ago. Ever since then she has been randomly walking up to me and demanding that I kiss various body parts. Usually a dirty little foot (she hates socks) or a sticky little hand. Sophia currently has a scratch on her hand that she has demanded that I kiss so often that I put a bandage on it. Of course it didn't stay on and I'm back to having to kiss her hand several times an hour.