Objective : To investigate the effect between Fructus Immaturus Ponciri (FIP, the immature fruit of Poncirus trifoliata) and Fructus Ponciri (FP, the ripe fruit of Poncirus trifoliata) on mast cell-mediated immediate-type allergic reactions. Methods : We performed anaphylactic reaction, histamine release, cAMP, $TNF-{alpha}$, IgE. Results : The aqueous extract of FIP dose-dependently inhibited systemic and local allergic reaction was induced by compound 48/80 or anti-dinitrophenyl (DNP) IgE in a murine model. FIP also significantly inhibited mast cell-dependent ear swelling response induced by topical application of compound 48/80. When mice were orally pretreated with FIP, the plasma histamine levels were reduced in a dose-dependent manner. FIP dose-dependently inhibited histamine release from the rat peritoneal mast cells (RPMCs) was activated by compound 48/80 or anti-DNP IgE. The level of cAMP in RPMCs, when FIP was added, increased compared with that of a normal or control. In addition, FIP had a significant inhibitory effect on anti-DNP IgE-induced tumor necrosis factor-a ($TNF-{alpha}$) production from the RPMCs and IgE produced by lipopolysaccharide-stimulated murine whole spleen cells or U266B1 as human IgE-bearing B cells. However, FP showed the lower inhibition rate than those of FIP in above all allergic reactions. Conclusion : These data have important implications for our understanding of the clinical effects of FIP and FP on allergic diseases, and FIP is more effective than FP on the allergic reaction.