This study investegated the effect of Liriope platyphylla (LP) on allergic reactions and its mechanism of action. We investigated the effect of LP on Evans Blue (EB) extravasation induced by anti-dinitrophenyl (DNP)-IgE in rats. We tested whether the ethanol extract of LP reduced ear skin thickness and historical changes induced by topical application of 2,4-dinitrofluorobenzene (DNFB) to ears of mice. We evaluated compound 48/80-induced release of histamine in rats peritoneal mast cell (RPMCs). We also investigated the regulatory effect of LP on the level of inflammatory mediators in PMACI-induced human mast cell (HMC-1); cytokine IL-6, IL-8, TNF-${alpha}$ in HMC-1, MAPKs (ERK, JNK and p38) in HMC-1. The ethanol extract of LP (81.3 mg/100 g body weight) significantly inhibited the PCA reaction compared with the control (P < 0.05). However, LP did not prevent topical applications of DNFB-induced ear skin thickening and histological changes. In RPMCs, histamine release induced by compound 48/80 was significantly attenuated by LP at $100{mu}g/ml$ (P < 0.05). LP extract ($100{mu}g/ml$) significantly reduced the PMACI-induced IL-6, IL-8, and TNF-${alpha}$ secretion via inhibition of ERK phosphorylation in HMC-1. In conclusion, the ethanol extract of LP inhibited mast cell-derived, immediate-type allergic reactions, and the result suggest the potential of LP for preventing allergic inflammatory disorders.