Acne is caused by having too much of a natural oil in your skin called sebum and dead skin cells that block your hair follicles. Your skin can produce too much oil during your teenage years due to changes in your hormones. Certain things can increase your chance of developing acne, such as having polycystic ovary syndrome, and taking medicines such as corticosteroids. Acne can also run in families.
See our section: Causes of acne above for more information.