Acne is the result of overactive oil glands at the base of hair follicles, which are a cause of hormonal changes during adolescence.
Oily skin can be hereditary, which increases the sensitivity of the skin to hormonal changes.
Contrary to belief, acne is not caused by eating oily foods, soft drinks, or chocolate. Likewise, acne does not indicate that the teen's face is too dirty. Family background or heredity plays a very important role as well. If the skin cells that line the oil glands or pores are present in unusually large numbers, they tend to stick together, clogging the openings to the pores, leading to whiteheads or blackheads. Bacteria thrive on this oil from oil glands, growing readily beneath the skin cells and leading to infection.