At puberty, the oil glands of the skin start producing an oily material called sebum, which lubricates the skin. Sometimes the wall of the oil gland breaks and spills the sebum within the skin, causing redness, swelling, and pus - in other words, a pimple. Plugged oil glands may form blackheads and whiteheads.

There is a type of bacteria that normally lives on the skin called Propionibacterium acnes. This bacteria lives on the sebum produced by the skin’s oil glands. Sometimes, this bacteria multiplies, resulting in inflammation and acne. Acne is built into an individual’s genes and tends to run in families. In women, acne often worsens at the time of menstruation. Foods do not cause acne, but for some people, certain foods, such as chocolate, nuts, carbonated beverages, and milk, can make acne worse. Acne may also become worse when one is under stress, and certain ingredients in cosmetics can aggravate acne.