['Mast cell-derived histamine is known to act on dermal fibroblasts and contribute to formation of an intractable chronic allergic dermatitis. Although this fibrotic event may also occur in other organs such as the nasal mucosa, no direct evidence has been reported as to whether responsiveness to histamine by fibroblasts derived from different organs is of the same intensity. Furthermore, while type 1 histamine receptor (H1R) blockers have been shown to be effective for alleviation of the symptoms of allergic diseases, their ability to affect histamine-induced tissue remodeling has not yet been clarified.', 'Our aim was to study the effect of H1R-blockers on histamine-induced tissue remodeling.', 'A macroarray assay was used for a comprehensive analysis of histamine-induced gene expression by normal human fibroblasts. Fibroblasts derived from skin or nasal mucosa were cultured in the presence of various concentrations of histamine, and the synthesis of type 1 collagen was measured by means of semi-quantitative reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. To determine the effect of H1R blockers, diphenhydramine hydrochloride and emedastine difumarate were investigated in this assay.', 'Histamine induced expression of various kinds of fibrogenic molecules in fibroblasts. Increased type 1 collagen expression was observed in fibroblasts treated with high-dose (0.1 mM to 1 microM) and low-dose (1 pM) histamine. This histamine-induced type 1 collagen synthesis was effectively diminished by emedastine difumarate. While organ specificity seems to be involved, emedastine difumarate is considered to be an effective drug for reversal of such histamine-induced remodeling in the skin.'] Does emedastine difumarate inhibit histamine-induced collagen synthesis in dermal fibroblasts?