In a variety of skin diseases, tissue eosinophilia is observed. However, the mechanism of eosinophil infiltration into the skin remains to be clarified. Interleukin-5 (IL-5) is well known as an important eosinophil chemotactic factor. To date, a number or chemokines that potently chemoattract eosinophils, such as eotaxin, eotaxin-2, eotaxin-3, regulated upon activation in normal T-cells expressed and secreted (RANTES), macrophage inflammatory protein-1 α (MTP-1 α), monocyte chemotactic protein-3 (MCP-3), MCP-4 and MCP-5 have been reported. Among them, eotaxin is a selective and strong chemoattractant for eosinophls in vitro and in vivo. Local administration of eotaxin induces eosinophil accumulation in the skin, lung, and peritoneal cavity. IL-5 expression is observed in most skin diseases with tissue eosinophilia, including atopic dermatitis, bullous pemphigoid, and malignant lymphoma. Recently, eotaxin expression has also been demonstrated in atopic dermatitis, bullous pemphigoid, drug eruption, and malignant lymphoma. Cooperation between IL-5 and eotaxin is reported to strongly induce eosinophil infiltration into skin. IL-5 and eotaxin may be the most important factors in eosinophil accumulation in the skin.