A sensor told a lie
Why Does Mint Feel Cold?
Mint lowers the temperature of nothing at all. It switches on the nerve that reports cold.
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Step 1 of 5
Your mouth has a separate sensor for cold.
Nerve endings in your tongue and lips carry a protein that opens when the temperature drops below about 26 degrees. When it opens a signal goes up, and your brain calls it cold.
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Step 2 of 5
Menthol opens that sensor without any cooling.
Menthol is the main oil in mint, and it fits the cold sensor's own switch. It pulls the sensor open at ordinary mouth temperature, so the nerve fires as though the temperature had fallen.
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Step 3 of 5
A thermometer disagrees with your mouth.
Nothing cooled. The sensor sent the message anyway. Hold a thermometer under your tongue, chew a mint and watch the reading. It does not move. Nothing has cooled — what changed is the reporting, not the temperature.
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Step 4 of 5
Breathing in makes it much stronger.
Air moving over a wet surface does cool it a little. With the sensor already held open, that small real chill is read as a large one, which is why a mint bites hardest on an inward breath.
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Step 5 of 5
Chilli plays exactly the same trick backwards.
Capsaicin opens the heat sensor instead, which is why a pepper burns without being hot. Mint and chilli are one mechanism run in two directions.
The short version
Mint feels cold because menthol holds your cold sensor open — the nerve fires, the thermometer never moves, and chilli runs the identical trick on the heat sensor.
Try it yourself
Chew a strong mint, then breathe in through your mouth. The cold jumps, though that air was sitting in the room a second ago.