Acne vulgaris (or acne) is a common human skin disease, characterized by areas of skin with seborrhea (scaly red skin), comedones (blackheads and whiteheads), papules (pinheads), pustules (pimples), nodules (large papules) and possibly scarring. Acne affects mostly skin with the densest population of sebaceous follicles; these areas include the face, the upper
part of the chest, and the back. Severe acne is inflammatory, but acne can also manifest in noninflammatory forms. The lesions are caused by changes in pilosebaceous units, skin structures consisting of a hair follicle and its associated sebaceous gland, changes that require androgen stimulation.
Acne occurs most commonly during adolescence, and often continues into adulthood. In adolescence, acne is usually caused by an increase in testosterone, which people of both genders accrue during puberty. For most people, acne diminishes over time and tends to disappear — or at the very least decrease — after
one reaches one's early twenties. There is, however, no way to predict how long it will take to disappear entirely, and some
individuals will carry this condition well into their thirties, forties, and beyond.
Some of the large nodules were previously called "cysts" and the term nodulocystic has been used to describe severe cases of inflammatory acne. The "cysts," or boils that accompany cystic acne, can appear on the buttocks, groin, and armpit area, and anywhere else where sweat collects in
hair follicles and perspiration ducts. Cystic acne affects deeper skin tissue than does common acne.
Aside from scarring, its main effects are psychological, such as reduced self-esteem and, according to at least one study, depression or suicide. Acne usually appears during adolescence, when people already tend to be most socially insecure. Early and aggressive treatment is therefore advocated by some to
lessen the overall impact to individuals.