Kale (Brassica oleracea L.var.acephala DC) has been shown to alleviate the effects of pollinosis. However, very little is known about its effect on other allergic diseases. In this study, we examined the effects of dietary kale on single or chronic contact hypersensitivity (CHS) elicited by 2,4,6-trinitrochlorobenzene (TNCB) in mice. The application of kale reduced ear swelling and cell invasion in single CHS and chronic CHS. This ability was enhanced by a longer period of intake or higher dose of kale. In addition, kale reduced mast cell invasion in chronic CHS, but the total IgE levels in blood plasma were not changed by kale treatment. Therefore, the inhibitory effects of kale on ear swelling and cell invasion were related to mechanisms other than the production of IgE. Taken together, dietary intake of kale probably improved or relieved allergic dermatitis.