Caption

Back acne. Acne vulgaris on a 15 year old boy's back. Acne is a general name given to a skin disorder in which the sebaceous glands become inflamed. The most common form is acne vulgaris, which begins in adolescence and is due to overactivity of the sebaceous glands. Pustules (large red spots) are hair follicles blocked by sebum plugs that have become infected with the bacterium Propionibacterium acnes. It occurs mainly on the face, chest and back, and is more common in young men.