Acne vulgaris (acne) is a chronic and self-limiting condition that begins in adolescence and can last over 10 years. Acne is characterized by inflamed and noninflamed comedones, oily skin, and cysts. The mechanisms for the initial development of comedones are not fully understood. Four factors have been identified which contribute to acne lesions and are the main targets of treatment. These factors include follicular keratinization, sebum production, Propionibacterium acnes (P. acnes), and inflammatory mediator release. Acne lesions may involve cellular inflammation causing hyperkeratinization of follicular ducts. P. acnes can induce keratinocytes to produce cytokines which rupture ducts, causing comedones. Genetics and androgen imbalances can influence sebaceous gland lipid synthesis. Exacerbation can result from single or multiple factors such as P. acnes, menstruation, occupation, personal sweating, diet, or stress.