At the University of California , David Julius and his research team have been making some interesting discoveries involving tongue receptors and a substance contained in chili peppers. They found that this substance activates the same receptors that senses heat. In other words, by chemically activating the right receptors on the tongue, the chili pepper fools your body into thinking that it is sensing actual physical heat.
A similar experiment involving mints was also tried by Julius and his team. Since publishing their findings about the heat receptors, they have also discovered a cold-receptor. A second group, at the Scripps Research Institute, has reported the same finding. The same sensory receptors on cells that tell you when something is cold can be activated by particular chemicals, giving you the sensation of coldness when none is there. One chemical that works nicely is menthol. Now you know why mints make your mouth feel cold.