Capsaicin is the ingredient found in different types of hot peppers, such as cayenne peppers, that makes the peppers spicy hot. Prototype vanilloid receptor agonist (pEC50 values are 7.97 and 7.10 at rat and human VR1 receptors respectively). Activates sensory neurons that give rise to unmyelinated C-fibers, many of which contain substance P. Topical application desensitizes the sensory nerve endings giving a paradoxical antinociceptive effect. MW: 305.42. Purity ≥98% by HPLC