The main reasons for acne on the forehead are as follows: First, it is related to the high secretion of hormones, so acne mostly occurs in adolescents. If a girl’s menstruation is not very regular and accompanied by dysmenorrhea, she should pay attention to gynecological ultrasound and hormone levels to determine whether acne is induced by high androgens and polycystic ovary syndrome. Secondly, acne is mainly related to the secretion of sebaceous glands, that is, more oil production. Thirdly, acne is related to the infection of P. acnes bacteria, life and living, such as staying up late for a long time, eating spicy, fried and sweet food, smoking and drinking alcohol, etc., and not washing the face thoroughly enough every day.