The underlying cause of acne is unknown.

Four factors are responsible for the formation of acne:

• Overgrowth of the skin cells that line the skin pores, which plugs the pore
• Overproduction of skin oils, which also plug the pores
• Overgrowth of the bacterium, Propionibacterium acnes
• Inflammation of the skin

These factors cause the formation of the swollen whiteheads, blackheads and cysts in the skin.