Skin is a substantial immune organ and represents the most important barrier against the potentially hostile environment. Its first line of defense are effector molecules of the innate immune system, which in contrast to the adaptive immune system reacts immediately against penetrating pathogenic microbes. Antimicrobial peptides represent the basis of the phylogenetically oldest part of the immune system. New studies show that reduced local cutaneous expression of antimicrobial peptide in burned skin is involved in the higher incidence of wound infections. The epithelium has an essential function in recognizing colonies of micro-organisms and in initial antimicrobial defenses.