AbstractClinical observations show that patients with anorexia nervosa (AN) are surprisingly free from infectious diseases. There is evidence from studies in Drosophila melanogaster that starvation leads to an increased expression of antimicrobial peptides (AMPs). AMPs are part of the innate immune system and protect human surfaces from colonization with pathogenic bacteria, viruses and fungi. We compared the expression of AMPs between patients with AN and healthy controls (HC) and investigated the influence of weight gain. Using a standardized skin rinsing method, quantitative determination of the AMPs psoriasin and RNase 7 was carried out by ELISA. Even though non-significant, effect sizes revealed slightly higher AMP concentrations in HC. After a mean weight gain of 2.0 body mass index points, the concentration of psoriasin on the forehead of patients with AN increased significantly. We could not confirm our hypotheses of higher AMP concentrations in patients with AN that decrease after weight gain. On the contrary, weight gain seems to be associated with increasing AMP concentrations.