Younger children write on themselves to experiment the feel of the ink on their skin and to see how it looks on them. As kids get older, teens may write on themselves as a way of self-expressoin. It could be that your daughter's friends are doing the same thing. Especially since tattooing has become a norm in our society, many teens see it as an art form or as a way to express their beliefs and their personal identity.
It does not sound like it is a problem unless of course you feel the symbols she is drawing are inappropriate or vulgar in any way. You can keep discouraging her from writing on herself because some ink is not healthy for the skin. Encourage her to wash the ink off before she goes to bed or goes out. If she and other teens are doing this at school, the teachers may crack down on it and eventually prohibit them from doing it at school.
If you would like to speak with a counselor about this in more detail, please call or e-mail our Hotline. We are here 24/7 for parents and children of all ages. Take care and best wishes to you and your daughter!
Boys Town National Hotline