Acne on forehead may be caused by acne, folliculitis, sebaceous cysts and other diseases. 1. Acne: It is associated with heredity, androgen-induced sebum secretion in large quantities, Propionibacterium acnes infection, and abnormal keratinization of follicular sebaceous gland ducts. 2. Folliculitis: the cause of folliculitis is clearer and is caused by bacterial or fungal infection around the hair follicles. Excessive sweating, high temperature, scratching, poor hygiene, systemic chronic diseases and immune diseases can easily induce folliculitis. 3. Sebaceous cysts: the cause of sebaceous cysts is also relatively clear, is the sebaceous gland ducts blocked, secretions in the local collection caused. Infection, trauma, puberty and other factors are more likely to induce sebaceous cysts. To summarize, there are many reasons for forehead acne, if it can’t go away for a long time or further aggravate, it is recommended to go to the dermatology department of the hospital in time.