Hair grows on human skin in various textures, colors, and density. The structure from which each hair grows is called a follicle. Muscles, oil glands (sebaceous glands), and nerves extend from the follicle into the next layer of the skin — the dermis. Throughout life, the skin is constantly shedding dead skin cells and growing new ones. This happens all over the skin. Inside the follicles, sebum (oil) carries the dead cells to the surface. Various factors can interfere with the cycle of renewal and disposal, and a number of disorders can result. Folliculitis is infection and inflammation of the hair follicles. The condition may be superficial (i.e., on the surface of the skin) or deep within the follicles. Hair follicles become red and irritated, and pus-filled lesions form. Folliculitis can clear up by itself in a matter of a couple of weeks or become more persistent and thus require treatment.