Acne occurs when oils produced by the skin mix with dead skin cells and plug up hair follicles.
Bacteria can become trapped in the follicles and cause the follicles to swell. The air then causes it to turn black. If the wall of the follicle breaks, the area can swell and often becomes red. Non-prescription medications are effective at treating and preventing whiteheads and blackheads. Clearasil Adult Care TM contains sulfur.