Background: Eotaxin plays a central role in the development of allergic diseases such as atopic dermatitis (AD), asthma, and nasal allergy because it acts as a chemoattractant for eosinophils in allergic inflammation. The inflammatory cytokines interleukin (IL)-4, tumor necrosis factor-alpha, and IL-13 have been reported to enhance eotaxin production synergistically in normal human fibroblasts. Histamine is known to be an important mediator of allergic inflammation.Objective: In this study, we investigated the expression of eotaxin in the skin in AD, whether histamine induces eotaxin production by cultured human fibroblasts, and the effect of various doses of the histamine H 1 -receptor antagonist cetirizine on histamine-induced eotaxin production during a 72-hour period.Methods: After histamine stimulation of cultured fibroblasts, supernatants were collected to measure eotaxin by enzyme-linked immunosorbent assay and the cells were lysed for detection of eotaxin mRNA. Eotaxin expression was studied using immunohistochemical methods and the reverse transcription-polymerase chain reaction (RT-PCR).Results: Histamine enhanced eotaxin production and its mRNA expression in a dose-dependent manner. The histamine-receptor antagonist diphen-hydramine inhibited eotaxin production and mRNA expression. Similarly, cetirizine also blocked histamine and IL-4-induced eotaxin production and mRNA expression.Conclusions: These observations suggest that eotaxin may have an important role in allergic inflammation and that cetirizine may inhibit histamine-induced eotaxin production and its mRNA expression in human fibroblasts.