Acne can be caused by a combination of factors, including excess oil production, clogged pores, inflammation, and the presence of bacteria on the skin. Hormonal fluctuations, especially during puberty, menstruation, pregnancy, or certain medical conditions can also play a significant role in acne development. While bacteria like Propionibacterium acnes contribute to the formation of pimples, hormonal imbalances can influence oil gland activity, leading to the production of more sebum and contributing to acne. It is often a combination of both bacterial and hormonal factors that contribute to acne breakouts.