Whether you are a gum chewer or not, the following universal experience associated with chewing mint gum is not just unpleasant but outright painful: you pop in a fresh stick of gum, go to take a sip of cold water, and bam! The seemingly frigid water is about 15 degrees colder than normal, and feels freezing against your teeth and throat. Why does this happen?

Think of an optical illusion you have seen before, perhaps in a museum or on social media. Sensory illusions are not limited to vision. What is going on with the mint gum/cold water situation is a thermal illusion, in which your body’s temperature sensing is temporarily altered. 

The protein that is responsible for this illusion is called TRPM8, which is an ion channel that “regulates the movement of ions across membranes of cells… TRPM8 opens in the presence of cold temperatures and allows [sodium] and [calcium] to enter the cell.” This essentially sends a signal to the nervous system, telling it that your body is perceiving something cold and causing it to respond accordingly.

The ingredient in mint gum that is responsible for the trickery of this protein is menthol, a common cooling agent in mint-flavored products. “[It causes] the brain to perceive a temperature drop in your mouth, even though no physical temperature change occurs… When you drink something that is actually cold [like a glass of refrigerated water], your cold receptors go into overhaul and make it seem like your mouth is in an arctic freeze,” explains Medical Daily. 

Menthol remains in your mouth for a period after you dispose of the gum, so for a few hours after chewing , cool air or water will continue to cause the firing of neurons, leading to a prolonged feeling of thermal illusion.