Why are chile peppers so hot?
A. The compound capsaicin (cap-SAY-a-sin) is what causes the burning sensation. Capsaicin is mainly concentrated in the white pithy ribs inside the pepper, but a good amount can also be found in the seeds. Since they are indigestable by the human stomach and intestines, seeds can sometimes cause some discomfort the next morning when they’re, ahem, passed from the body.