Acne vulgaris is a chronic inflammatory disease of the pilosebaceous units. The etiologic factors include increased sebum production, ductal hyperkeratosis, abnormality of the microbial flora within the pilosebaceous unit, and chemomediators of inflammation. The dermal inflammation is not due to presence of bacteria, but from biologically active chemomediators produced by P. acnes and the microenvironment within the pilosebaceous unit, is probably more important than the absolute number of P. acnes organisms. Indeed, the major role of the sebaceous gland appears to be supplying nutrients needed by P. acnes and moreover, the microbiologic principle of biofilms appears to be applicable to P. acnes in acne.11