Chitosan is a deacetylated derivate (> or =50%) of chitin, to which antimicrobial properties have been assigned. As bacterial resistances to antibiotics are increasing, alternative treatments have been gaining in importance. In the present study, the authors investigated the antimicrobial effect of a chitosan-containing spray in a randomized, double blind, placebo controlled clinical trial at the department of dermatology of the University of Osnabrueck. Twenty-nine healthy volunteers applied a chitosan-containing (1% concentration, low molecular chitosan, degree of deacetylation 87%) spray and a chitosan-free control (vehicle only) spray to the left and right foot respectively for five days. Before and after treatment swabs were taken for microbiological analysis. Bacterial count of the chitosan treated areas showed a significant decrease (P<0.001) compared to those areas treated with the chitosan-free spray. Thus, chitosan might serve as an alternative local antimicrobial agent in the future.