Doctor injecting the anti-inflammatory steroid triamcinolone acetonide into a pimple on an 18 year old Hispanic male patients face. Acne is a general name given to a skin disorder in which the sebaceous glands become inflamed. The most common form, acne vulgaris, begins in adolescence and is due to overactivity of the sebaceous glands. Pustules are caused by the blockage of hair follicles by sebum plugs. Acne vulgaris occurs on the face, chest and back, and is more common in young men. Its mild form disappears in adulthood; more persistent, chronic acne results in infected cysts and scarring of the skin.