Acne is an inflammatory disease of the skin, caused by changes in the pilosebaceous units (skin structures consisting of a hair follicle and its associated sebaceous gland). Acne lesions are commonly referred to as pimples or zits. The condition is most common in puberty, especially among Western societies most likely due to a higher genetic predisposition. Excessive secretion of oils from the sebaceous glands combines with naturally occurring dead skin cells to block the hair follicles. There also appears to be in some instances a faulty keritinization process in the skin leading to abnormal shedding of skin lining the pores. Oil secretions build up beneath the blocked pore, providing a perfect environment for the skin bacteria Propionibacterium acnes to multiply uncontrollably. In response, the skin inflames, producing the visible lesion.