Acne is a skin condition characterized by plugged pores (blackheads and whiteheads), inflamed pimples (pustules), and deeper lumps (nodules). Acne often occurs on the face as well as the neck, chest, back, shoulders, and upper arms. Although many teenagers get some form acne, adults in their 20s, 30s, 40s or even older can develop acne. Often acne clears up after several years, even without treatment. However, untreated acne can lead to permanent scarring. Acne occurs when hormones trigger the sebaceous glands in the skin enlarge and produce oil, resulting in clogged pores. Acne treatments vary according to the type of acne that is present.