Capasicin, a neurotoxin extracted from red peppers, has selective effects on peptide-containing C-fiber and induces the release of neuropeptides from sensory nerve endings. Mast cells and neuropeptide-containing nerve fibers occur in close proximity throughout in the airway mucosa, around blood vessls in the smooth muscle, and beneath the epithelium. Capsaicin stimuli trigger these sensory nerve fibers to release neuropeptides, which may then initiate the process of neurogenic inflammation. Neurogenic inflammation denotes the vasodilatation and vascular permeability changes that follow neuropeptide-induced mast cell antivation. The purpose of this study was to determine whether capsaincin could induce mast cell activation in vivo. For this, effects of capsaincin on the ear swelling of mouse, degranulation of skin and mesenteric mast cells, and vascular permeability of rat in vivo were measured. We found that in vivo capsaicin induced the ear swelling of mouse, degranulation of skin and mesenteric mast cells in a dose-dependent fashion. Additionally capsaicin caused to increase of vascular permeability. These results suggest that capsaicin induces inflammation through activations of mast cell.