It doesn't hurt them at all. I shaved the hair off of the whole ear to prevent pulling the hair out. I will post a link to the directions I used and they work great. Both of their ears came up and stayed up for a week or so but they are teething. You just have to do it regularly until they don't fall anymore. leave the tape on for 3 days and then take it off and then if they start to fall tape them again for 24 hrs and then remove, keep doing this until they stay.
http://members.cox.net/jrogan/ears.html