Leukotrienes constitute a group of lipid mediators, which may be subdivided into two groups, with leukotriene B 4 on the one hand and cysteinyl leukotrienes on the other. Although leukotrienes are abundantly expressed in skin affected by diverse chronic inflammatory diseases, including atopic dermatitis, psoriasis, pemphigus vulgaris and bullous pemphigoid, their pathological roles in these diseases have remained elusive. Recent data now reveal that both leukotriene B 4 and cysteinyl leukotrienes are indispensable in the pathogenesis of atopic dermatitis, with leukotriene B 4 initiating the recruitment of inflammatory cells, particularly neutrophils and T H 2 cells into the skin, and cysteinyl leukotrienes later inducing characteristic structural alterations of chronically affected skin, specifically skin fibrosis and keratinocyte proliferation. Thus, these results reveal a sequential cooperation of LTB 4 and cysteinyl leukotrienes to initiate and perpetuate allergic skin inflammation. These new insights highlight leukotrienes as promising therapeutic targets in allergic skin inflammation and should encourage more research into the role of leukotrienes in other inflammatory skin diseases.