Some lesions are deep-seated and can cause scaring.
Predisposing factors known to influence acne include hereditary tendencies and disturbances in the androgen-estrogen balance. External factors can include exposure to halogens, vitamin deficiencies, exposure to certain chemicals such as tar and chlorinated hydrocarbons, etc. Acne normally begins at puberty, when the body increases secretion of androgen in both males and females, thereby increasing the size and activity of the pilosebaceous glands. In females the lesions may worsen just before menstruation. Bacteria are known to worsen existing acne, which explains the benefit some sufferers receive from antibiotic therapy.