Acne is a very common skin condition characterised by comedones (blackheads and whiteheads) and pus-filled spots (pustules). It usually starts at puberty and varies in severity from a few spots on the face, back and chest, which most adolescents will have at some time, to a more serious problem that may be embarrassing, sap self-confidence and cause scarring. For the majority it tends to resolve by the late teens or early twenties but can persist for longer in some people. Acne can develop for the first time in people in their late twenties or even the thirties. It occasionally occurs in young children.