This document discusses what causes acne and the different types of acne lesions. It explains that sebum from skin glands can clog pores, trapping bacteria and dead cells to cause acne lesions like whiteheads, blackheads, papules, pustules, nodules and cysts. Hormone changes during puberty are a main cause of acne outbreaks in teens. While acne can occur at any age, effective treatment options exist to minimize breakouts.