A total of 28 male BALB/c mice (average weight 20.7 +/- 1.6 g) were divided into 4 treatment groups and fed a commercial diet (A), a commercial diet + induced colitis by dextran sodium sulfate (DSS) (B), Inonotus obliquus (IO) administration (C), and IO administration + induced colitis by DSS (D). IO treatment (C, D) decreased the expression of tumor necrosis factor (TNF)-alpha and signal transducers and activators of transcription (STAT)1 compared to those of the colitis induced group (B). The expressions of IL-4 and STAT6 were decreased in group D compared to the colitis induced group (B). The serum immunoglobulin (Ig)E level decreased in IO treatment groups (C, D) compared to no IO treatment groups (A and B) although there was no significant difference between the IO treatment groups. Extract from IO itself had a weak cytotoxic effect on murine macrophage cell line (RAW264.7 cells). Extract from IO inhibited lipopolysaccharide- (LPS-) induced, TNF-alpha, STAT1, pSTAT1, STAT6, and pSTAT6 production in RAW264.7 cells.