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.