Chili peppers create a burning sensation in your mouth because they are actually thermally hot.
The burning sensation from chili peppers is not actual heat but a chemical effect. Capsaicin, the compound in peppers, binds to pain receptors (TRPV1) that normally respond to heat, triggering a false pain signal. Your mouth isn't actually hotter after eating peppers; the burning sensation is a sensory illusion created by tricking pain receptors.
Reception
Sources
- Nature: Capsaicin and TRPV1 PRIMARY
- Journal of Neuroscience: Pain Receptors PRIMARY