hi, i understand your concern. but acne may be caused by dandruff, irregular mentrual cycles ( pcos), food habits, etc. mostly forehead acne is due to dandruff. so better you use ketoconazole based shampoo for your hair along with anti acne medications like tretin, clindamycin and benzyl perixide for your acne
Next Steps
do regular hair washes atleast thrice a week
Health Tips
avoid junk, diary products, oily foods