The mystery of minty coolness

The answer does not lie in any actual change in temperature, but in a kind of “sensory trick” involving your nervous system. The key player in this phenomenon is a natural substance called menthol, found in mint plants. Menthol is not simply a flavour, but a molecule capable of interacting with specific receptors in our bodies responsible for sensing cold. These receptors are called TRPM8 and are found on the nerve endings in the mouth, the skin and even the airways. When menthol binds to these receptors, it changes their shape, opening channels through which particles such as calcium can enter. This change in shape and the passage of charges triggers a nerve signal that reaches the brain. The brain interprets this signal as a drop in temperature, even though there has been no real cooling in your mouth. The way menthol “tricks” the brain is similar to the way chilli peppers affect heat receptors. Just as capsaicin in spicy foods makes us feel intense heat, menthol activates cold receptors. The difference is that, in neither case does the actual temperature change: what changes is the signal sent to the brain, telling your body “I am cold” or “I am hot”. This scientific explanation helps us understand why, after using a mint-flavoured product, a simple sip of water can feel incredibly cold. Menthol has already activated the TRPM8 receptors, and when it comes into contact with cooler liquids or air, those receptors respond even more strongly. The overall effect is a sensation of cold that far exceeds physical reality. Menthol, however, is not limited to creating a pleasant sensation in sweets or toothpaste. Companies exploit this property to give oral hygiene products such as chewing gum, mouthwash and toothpaste a feeling of freshness and cleanliness, because that sensation of coolness is associated with the idea of deep cleaning and fresh breath. In addition, in sweets and throat products, the cooling effect can create the impression of more open airways, even though it does not actually alter airflow. Another interesting application of menthol concerns sport. Some studies have observed that rinsing with a menthol solution can make athletes running in high temperatures feel less hot. Even if body temperature does not decrease, the sensation of freshness may help improve performance because the brain does not perceive thermal stress in the same way. However, this use is still being studied and debated by experts, especially because it could lead some people to push their bodies beyond safe limits without realising it. Menthol can also have a local effect on the skin and muscles. In many pain-relief creams, menthol is an important ingredient because, by activating receptors similar to those involved in sensing cold, it can act as a kind of “counter-irritant”: a temporary cooling sensation that distracts from the underlying pain, providing relief in cases of muscle or joint pain. It is fascinating to think that this distinctive feeling of freshness is actually a sensory illusion, generated by the way menthol communicates with the nervous system rather than by any physical change in temperature. The next time your mouth feels icy after a mint sweet, or after a sip of water following toothbrushing, you may remember that your brain is receiving a special message, interpreted as cold even in the absence of any real chill.