Traditionally Arnica montana L. is indicated for treatment of blunt injuries like strains, bruises and contusions that are physiologically accompanied by local inflammation and edema, including activation of the NF-kB pathway and the release of pro-inflammatory prostaglandins and leukotrienes that are produced by cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LO). Arnica flowers (A. flos) contain compounds, e.g. sesquiterpene lactones like helenalin or dihydrohelenalin that are known anti-inflammatory compounds. Here we aimed to evaluate the anti-inflammatory efficacy of a hydroethanolic extract from A. flos.