Botanically, there is no difference between hot peppers and sweet peppers – both are derived from species of Capsicum. Most come from C. annuum, but others are derived from C. frutescens, C. chinense (the source of the hottest peppers), C. pubescens and C. baccatum. A pepper’s heat is only partly controlled by genetics, environment also plays a role. Peppers grown at hot temperatures up to 95˚F tend to be the hottest, especially if they have been subjected to drought stress and fairly poor soil.
In 1912 Wilbur Scoville designed a scale to help determine the intensity of peppers and he rates them in Scoville heat units. The hotter the pepper, the greater the number of Scoville units. The average bell pepper contains 0 units and banana peppers, with 1,000 to 5,000 units, are considered mild. Habanero peppers (C. chinense), the hottest commonly grown type, rate between 100,000 – 1,000,000 units or more. They can be so hot they’ll burn your fingers when you harvest them. The Guinness Book of World Records rates the ‘Carolina Reaper’ at 2.2 million Scoville units!
When handling the fruit of the hot pepper plants, you may want to consider wearing gloves as the capsaicin in the fruit of these plants creates a pleasure/pain response in the mouth, but it burns the skin and eyes. Never touch your face near your eyes, mouth, or nasal passages. The capsaicin starts getting hot as the plant matures – around week 4. If you experience burning on the skin, rinse the affected area with whole milk until you experience relief. Capsaicin dissolves easily in fat or alcohol – but not in water. If you eat too fiery a pepper, get some relief by eating yogurt, ice cream, or milk.