Have you ever set your mouth on fire by biting into a chilli pepper? The sensation is caused by capsaicin, a chemical compound that stimulates the mouth’s pain receptors, which in turn tell the brain you’ve eaten something hot. The body reacts by perspiring and releasing endorphins, the “feel-good” effect of which perhaps accounts for spicy food’s appeal. The first scale for measuring a chilli’s heat was developed in 1912 by the chemist Wilbur Scoville. Scoville Heat Units refer to the number of times a chilli must be diluted before it is undetectable to tasters. The world’s hottest chilli, the Indian-originating “naga jolokia”, measures 970,000 SHU. Today a chilli’s heat can be measured more accurately using high-pressure liquid chromatography, a technique that calculates the concentration of capsaicin in a solution. Humans have consumed chillies for over 8,000 years, but they were first cultivated 6,000 years ago in South and Central America. In the late 15th century Christopher Columbus introduced chillies to the rest of the world for the first time, where they were called peppers because they were spicy like peppercorns. In addition to their culinary uses, chillies have long been prized for their medicinal properties. Scientific studies show that capsaicin may lower blood pressure and aid weight loss. Capsaicin has traditionally been used in tropical analgesics, however new research indicates that the compound may actually be carcinogenic.