Acne is the term for pimples and complexion problems which occur in young people and some adults. Pimples usually occur on the face, but may involve the neck, chest, back and upper arms. Acne is only a skin problem and does not affect your general health.
Sebum lubricates the skin.
Sometimes the wall of the oil gland breaks and spills the sebum within the skin which causes redness, swelling, and pus - in other words a pimple. Plugged oil glands may form blackheads and whiteheads. Blackheads are not caused by dirt. There is a bacteria that normally lives on the skin called Propionibacterium acnes . This bacteria lives on the sebum produced by the skin oil glands.