Despite a widely held belief that a large cause of acne is poor diet and lifestyle, there is little evidence to support this. Specialists believe that the main cause of acne is hormonal imbalances, which explains why teenagers are among the main sufferers. According to the University of Maryland, acne--official name, comedones--forms when the sebaceous glands in the skin produce too much sebum. This combines with debris and dead skin cells to clog the hair follicles. These then either seal over and become whiteheads, or are left open and become blackheads.