As anyone who has ever eaten a really hot chilli will testify, they can cause a lot of pain.
Chillies come in many shapes, colours, sizes and strengths, but one thing they have in common is the burning sensation they cause in your mouth, eyes and any other part of your body into which their juices come into contact.
Although most people think that the hottest part of a chilli is its seeds, in fact it is the white spongy layer you find inside, called the placenta. Bite into this and you will really feel the burn.
That burning sensation is mainly caused by a chemical called capsaicin, which is found in tiny glands in the chilli’s placenta.
When you eat a chilli, the capsaicin is released into your saliva and then binds on to TRPV1 receptors in your mouth and tongue.
The receptors are actually there to detect the sensation of scalding heat.
Capsaicin makes your mouth feel as if it is on fire because the capsaicin molecule happens to fit the receptors perfectly.
When this happens it triggers these receptors, which send a signal to your brain, fooling it into thinking that your mouth is literally burning.
The reason why wild chilli plants first started to produce capsaicin was to try and protect themselves from being eaten by mammals like you.
From an evolutionary perspective the plant would much rather have its seeds dispersed far and wide by birds.
Oddly enough birds, unlike mammals, don’t have TRPV1 receptors, so they do not experience any burn.
Read more – bbc.com