 The pathogenesis of acne is complex and understood only in part. The follicular occlusion with adherent keratinocytes and activation of hormone secretion resulting in the formation of sebaceous microcomedão. Studies suggest that free fatty acids intrafoliculares control inflammation through chemotactic properties on leukocytes, monocytes and neutrophils. The free fatty acids may provide the primary stimulus for the retention hyperkeratosis follicularis. Moreover, tallow provides a favorable substrate for the proliferation of Propiniobacterium acnes P. acnes. Studies suggest that P. acnes, a microaerophilic bacterium almost anaerobic, Gram-positive, has a lipase able to hydrolyze triglycerides in sebum into free fatty acids. Therefore, these pathogens play critical role in the generation of inflammatory lesions. The P. acnes produces proteases and neuroaminidases, which may increase the permeability of the follicular epithelium. Also produce a chemotactic factor of low molecular weight that selects the polymorphonuclear leukocytes. In the process of phagocytosis of bacteria are released hydrolases, which break the integrity of the follicular wall. Subsequently, the content intrafolicular - fragments of keratin, fat, hair, and P. acnes - is expelled to the dermis. 