The active ingredient in hot peppers is capsaicin. It causes irritation and also stimulates the mucous membrane of the mouth, stomach and bowels causing, peristalsis.
Capsaicin causes a sensation of burning in any tissue it comes into contact with, by activating the heat receptors in human nerve endings, (don’t touch your eyes when handling hot pepper) It also stimulates secretion of the nose, eyes and sinuses. Consumption of hot pepper causes sweating of the body, which results in a cooling effect in hot climates.
The amount of heat in hot pepper depends on the cultivar and the age of the pepper. The more mature the pepper, the hotter it will be. Red peppers are hotter than the green immature peppers.
The soil, climate and other conditions also affect the capsaicin content in peppers. Peppers of the same cultivar can vary in hotness depending on where they’re grown.
Measurement of Heat
The amount of heat in hot pepper is measured by the Scoville scale, which measures the pungency (spicy heat) of chilli peppers, recorded in Scoville heat units. The units range from 0 (Bell pepper); 100-900 (Paprika, Pimento); 3,500-10,000 (Chipotle, Jalapeño); 30,000-50,000 (Cayenne, Tabasco), 100,000-350,000 (Habanero, Scotch bonnet) to 2,000,200 (Carolina Reaper).