Forehead pimples belong to acne, the body’s androgen secretion, as well as hair follicle oil secretion increase, Propionibacterium folliculorum reproduction and so on related. 1. Excessive secretion of androgens in the body: Excessive secretion of androgens in the body or abnormal metabolism of hormones in the body can easily cause acne. 2. Increased oil secretion from hair follicles: Increased oil secretion from hair follicles will easily cause congestion and swelling of hair follicle ducts, which will induce acne. 3. Propionibacterium folliculare reproduction: Various reasons stimulate the reproduction of Propionibacterium folliculare, which stimulates the inflammatory response to make the follicle wall damaged and ruptured, and also induces acne. Acne on the forehead should be examined in a timely manner to determine the cause of the disease and take treatment measures as prescribed by the doctor.