The human tongue has 10,000 taste buds programmed to recognize five basic flavors: sweet, salty, bitter, sour, and savory umami. So when we’re eating a fiery papaya salad or blazing bowl of Texas red, how do those taste buds detect spice? The answer is capsaicin, a compound found in most members of the chile pepper family, likely as a deterrent to animals in the wild. Because the tricky truth of spice is that it’s not actually a flavor—it’s the sensation of pain from a chemical irritant, similar to poison ivy.
This is why you can feel a pepper’s sting on your fingers after handling chiles, and why you always should wash your hands thoroughly after doing so. Other compounds in chiles account for the actual taste and aroma of spicy food, but when it comes to the spice itself, you’re feeling the burn quite literally.