My mare used to rub multiple times a day, every day. The barn owner got a bit irritated because she kept pushing her stall door out by rubbing her butt on it!
I thought she just liked having her butt scratched, but we decided to put some dairy dust on the top of her tail. Took care of the problem overnight! She hasn't bought the stall down with her scratching since!
It's definitely something you can try, as it's usually a cheap product to obtain.