Capsaicin is a chemical substance. It is responsible for the sense of "spiciness" or "hotness" found in chili peppers. In mammals, it causes a sensation of "burning" of the tissues it comes in contact with. Capsaicin, and other similar substances called capsaicinoids are produced by chili peppers and other plants, probably as a protection against being eaten. Pure capsaicin is a hydrophobic, colorless, odorless, crystalline to waxy compound.