My Child Is A 13-year-old Girl. She Has Oily Skin.

My child is a 13-year-old girl. She has oily skin. She has acne that never seems to go, mostly on her forehead. Sometimes She gets styes as well, but they are not so severe and usually go within some days, maybe a week. She also have acne on my chest and back. We have gone to many dermatologists but none of them can give a solution that could give her at least one acne-free day.
Is there something I can do (home remedies, any medicines) for making the acne go away?