The histamine H4 receptor (H4R) is the newest receptor identified of four histamine receptors. Its expression in numerous immune and inflammatory organs has been implicated in relation to immune systems and allergic diseases. In the present study, we demonstrate the expression of H4R in human dermal fibroblasts and investigate changes in its expression level when stimulated by histamine, phorbol 12-myristate 13-acetate (PMA), lipopolysaccharides (LPS), dexamethasone and indomethacin. Histamine and PMA showed no effects on H4R expression. LPS and indomethacin up-regulated H4R mRNA expression, and 20 microM dexamethasone increased H4R protein levels. These results indicate a good prospective for this new receptor in the development of effective treatments of inflammatory diseases and pruritus or for the appropriate prevention of toxicities.