Acne is a skin condition that consists of comedones, papules, pustules, and cysts. Acne most commonly develops on areas of the body that contain a lot of sebaceous glands (oil) glands like the face, neck, chest, back and shoulders. Acne usually begins (and is most common) in puberty, but many adults also develop the condition. Acne is caused by three major factors: Blockage of hair follicles (pores), where sebum (oil) is produced, by dead skin cells Overproduction of sebum Proliferation of P. acnes bacteria and consequent inflammation