Y Arnica montana, of the family Asteraceae, is used for its anti-inflammatory and wound healing properties, especially for bruises, tissue injuries and other traumas. However, its cellular and molecular mechanisms are not yet fully known. Its main active ingredient is helenalin, a sesquiterpene lactone, known as one of the main active ingredients of Asteraceae species. The aim of this study was to investigate cell proliferation, wound healing and anti-inflammatory activity of helenalin on human keratinocyte cells treated with lipopolysaccharide stimulated human monocytic cell line. Human keratinocyte cells were treated with different helenalin concentrations (0.095-50 mu M) to determine toxic and nontoxic concentrations. Then, the effects of nontoxic (0.02 and 0.2 mu M) and toxic (2 mu M) helenalin concentrations on human keratinocyte cell proliferation and migration were determined using the real time cell analysis system. The scratch assay was performed to determine wound healing activity and supernatants were collected to determine the effects of helenalin on cytokine levels of human keratinocyte cells under inflammatory and non-inflammatory conditions. Under inflammatory conditions, 0.02 and 0.2 mu M helenalin increased keratinocyte proliferation and induced the most wound healing and anti-inflammatory activity in human keratinocyte cells. Cell proliferation and migration, wound healing and anti-inflammatory effects were higher in cells exposed to 0.02 mu M helenalin than 0.2 mu M. Helenalin has been found to decrease the production of inflammatory cytokines, especially under inflammatory conditions and increase wound closure by increasing cell proliferation and migration.