Shishihakuhito is a traditional Chinese medicine that is effective in the treatment of pruritic skin diseases of the elderly and atopic dermatitis. However, the molecular mechanism of such a beneficial action of shishihakuhito on the dermatologic disorders is unknown. In the present study, we for the first time examined whether shishihakuhito extract exhibits the inhibitory action on IgE-mediated histamine release from the rat basophilic leukocyte cell line, RBL-2H3 cells. The extract decreased IgE-mediated histamine release at 30 μg/ml, and more potently inhibited the histamine release at the concentrations of more than 100 μg/ml, with almost abolishing it at 200-400 μg/ml. Shishihakuhito consists of Gardenia Fruit, Phellodendron Bark and Glycyrrhiza. Next, to address the question of which crude drug components of shishihakuhito are responsible for the inhibitory action on IgE-mediated histamine release from RBL-2H3 cells, the activity of the Kampo preparations excluding each bulk extract of the shishihakuhito to inhibit the histamine release from RBL-2H3 cells was examined. The Kampo preparations without Gardenia Fruit or Glycyrrhiza at 100 μg/ml still prevented the histamine release, whereas that without Phellodendron Bark failed to inhibit the histamine release, demonstrating that Phellodendron Bark extract is mainly involved in the inhibitory action of shishihakuhito extract. In addition, shishihakuhito extract and the Kampo preparations excluding each bulk extract of the Kampo medicine inhibited lipopolysaccharide (LPS)-induced stimulation of NF-κB-dependent transcription in C6 rat glioma cells. These results suggest that shishihakuhito may exhibit the in vivo antagonistic action on allergic inflammation by inhibition of histamine release as well as LPS-induced stimulation of NF-κB-dependent transcription.