Objectives : Haedoksamul-tang (HSTE), a water extract from a mixture of Phellodendri Cortex, Coptidis, Scutellariae Radix, Gardeniae Fructus, Angelica acutiloba Radix, Cnidii Rhizoma, Paeoniae Radix, Rehmanniae Radix, has been traditionally used for allergic skin diseases such as atopic dermatitis and contact dermatitis in oriental countries. However, little is known about the effects of aqueous extract of HSTE on trimellitic anhydride (TMA)-induced contact hypersensitivity (CHS) in a mouse model. Methods : In this study, we investigate the pharmacological effects of HSTE on TMA-induced CHS in Balb/c mice. Contact hypersensitivity was induced in mice by topically sensitizing and challenging with TMA in flank skin and ears during oral administration (for 17 days) and topical treatment (30 min before challenge) with HSTE. We examined the effects of HSTE on IgE and IgG1 levels, inflammatory parameters in ear tissues, CD4+/CD8+ ratio, cytokine and chemokine production in sera, tissues, and immune cells from TMA-sensitized mice.Results : Oral and topical administration with HSTE reduced, in a dose dependent manner, thickness and leukocyte infiltration of ear tissues and IgE levels in serum from mice sensitized with TMA. In addition, auricula lymph node cells isolated from TMA-sensitized mice significantly elevated the expression ratio of CD4+/CD8+ as well as increased the production of IL-4, IL-5, IL-13 and IFN-γ by ex vivo stimulation with antibodies against CD3 and CD28, and these inflammatory indexes, except for IFN-γ, were significantly suppressed by orally and topically administration of HSTE. Furthermore, stimulation of auricula lymph node cells from TMA-sensitized mice with antibodies against CD3 and CD28 increased the production of MCP-1/CCL2 and MIP-1α/CCL3, and these effects were inhibited in a dose-dependent manner in cells from mice treated with HSTE. Conclusions : These results suggest that HSTE can be used for treating contact hypersensitivity by inhibiting leukocyte infiltration as well as production of serum IgE and chemokine/Th2 cytokine in an animal model.