Chilli heat is a group of complex chemical compounds called capsaicinoids that are responsible for giving Chillies their bite
Capsaicin is the most famous (and the most pungent) although scientists have identified and isolated other natural members of this fiery family Dihydrocapsaicin, Homodihydrocapsaicin, Nordihydrocapasaicin and one synthetic cousin Vanillyamide
The latter is used as a Calibration point for determining the relative pungency of the others
Capsaicin & Dihydrocapsaicin are typically responsible for about 80-90% of the capsaicinoids content of a pepper and hence are the source of most of the heat
The balance of the bite is made up by the presence of one or more minor capsaicinoids
Thats the Science Part - This is what Happens when you eat one
When Chillies are eaten, the capsaicinoids irritate the trigeminal cells or pain receptors located in the mouth, nose and stomach, which release a chemical known as substance P into blood which tells the brain you’ve eaten something not right
The brain responds by flushing the body with water, creating a heat feeling in the effected areas as a warning to you to stop eating
So the Sweating, Sniffles, Eye Watering and Saliva Production is the body trying to evict the hot chilli heat that you have just eaten
However, the trigeminal cells are also connected to the production of endorphins which produce a sense of well-being and happiness
It is the rush generated from the release of endorphins that is often cited as the reason why some Chilli Heads become addicted to fiery foods
Repeated consumption of Chillies is also believed to confuse trigeminal cells, which is also why some of the Chilli Fiends build up a tolerance to capsaicin and can, eat the hottest types without running to the nearest dairy farm faster than a speeding train!