It is not dangerous...girls that young are still growing. It just doesn't make sense for them to screw around with it at that age and that is why it is not recommended. St HErb in particular has a policy of trying not to upset the natural flow of things....cycling the pills, using for menopause hormone replacement etc....natural...and that does include letting nature take it's course with young women under 18 or so...even 20 they say. HAving said that I do know some girls in there very late teens want to and do try them. We all must take responsibility for our own bodies. etc. etc.