Why does menthol feel cool?

HAVE YOU a summer cold? Being all blocked up or having a sore throat isn’t fun, but one popular way to help ease the symptoms is to use menthol, a chemical naturally found in mint, which feels cool when you inhale it or take it in a lozenge.

Meanwhile, the cooling effect of menthol-containing gels can also help to bring relief from aches.

But have you ever wondered why a substance in a lozenge, vapour or rub at room temperature can give you the sensation of being cold?

The key, it seems, is a molecule in the body called the TRPM8 receptor, which is involved in sensing cool temperatures. That molecule sits at the membrane, or outer envelope, of sensory cells and it regulates the flow of electric charge across the membrane.

Simply put, menthol binds to the TRPM8 receptor and results in a signal being sent to the brain, which registers it as “cool”.

The discovery of the TRPM8 connection is relatively recent – key papers started to come out about 10 years ago – and since then research has been unravelling more about the enigmatic receptor.

“TRPM8 has an emerging role in a variety of biological systems, including thermoregulation, cancer, bladder function, and asthma,” states a paper last year in Current Pharmaceutical Biotechnology. The authors add that “ . . . it remains to be seen how this single ‘cool’ molecule can serve in such a multitude of biological processes.”