The itching we experience when eating chili peppers or hot peppers is due to a chemical compound called capsaicin.

Capsaicin activates pain receptors in the tongue and mouth, sending a signal to the brain that it interprets as a stinging or burning sensation. As the concentration of capsaicin increases, the intensity of the itching sensation increases.

Interestingly, capsaicin does not produce a specific taste, but rather stimulates pain receptors independently of the taste of food.

But why do plants produce capsaicin? Its function is believed to be to protect the plant from herbivorous predators, since mammals cannot tolerate the heat and avoid eating the chilies. However, birds are less sensitive to capsaicin and often feed on the chili peppers, thus helping to disperse the seeds.

The amount of capsaicin varies from one chili variety to another, and depends on factors such as maturity, cultivation, and environmental stress. Some varieties of chili are much hotter than others, due to their high concentration of capsaicin.

In short, chili peppers sting us because of the capsaicin. This chemical compound stimulates pain receptors in the tongue and mouth, creating a stinging or burning sensation. Capsaicin is produced by the plant to protect itself from herbivores, and its amount varies depending on the variety of chili.