Question of the Day: Why are bell peppers not spicy?
Quick Answer: Bell peppers are not spicy because they cannot produce capsaicin.
Capsaicin is an alkaloid compound produced by chili peppers to deter animals from eating them. It is also what makes hot peppers hot. The more capsaicin a pepper contains, the hotter it will be.
Bell peppers, completely lacking capsaicin, are not spicy.