The skin surface as antimicrobial barrier: present concepts and future outlooks.

Human skin protects the body as an outer barrier from various environmental threats and has to deal with an immense quantity of microbes comprising members of the own microbiota as well as potential pathogenic microbes. In this viewpoint, we highlight important cutaneous first-line defense barriers from the perspective of a microbe that tries to colonize and invade human skin. We place special emphasis on the role of antimicrobial peptides and the microbiota. In addition, we discuss and try to provide answers to some emerging issues concerning the various defense strategies of the epidermis.