Capsaicin

Capsaicin is responsible for the hot taste of chilli peppers and red peppers. It opens pain receptors on the tongue, which normally only respond to temperatures above 42 degrees Celsius. These receptors then send a signal, which creates a burning sensation.

Capsaicin is an alkaloid that occurs in some plants as a defence against being eaten by animals. It is not very water-soluble so if you bite into a hot pepper, drinking water won’t help. You would be better off eating full-fat yoghurt or taking a sip of wine because capsaicin does dissolve well in fat and alcohol.

There is also capsaicin in pepper spray. These sprays contain high concentrations – about 600 times stronger than ordinary pepper – that are extracted from different kinds of peppers. Ouch.