Acne is a chronic disease of the pilosebaceous follicle that affects mainly adolescents. It causes polymorph cutaneous lesions that may leave scars after regression. It is characterized by alternation of periods of exacerbation and stability. Spontaneous regression usually occurs after age 20, but some patients may continue suffering during adult life. Diagnosis is clinical and based on the patient's age at the time that the lesions first appear, and on its polymorphism and type of lesions and location. Some patients also need a hormonal and, sometimes, psychological evaluation. The right treatment for the right patient is key to treating acne safely.