Abstract

The ability to sense cold is essential for survival. Cooling agents such as menthol and its analogs that are often included in medicine, food, tooth paste and cosmetic formulations can cause cooling sensations. Although peppermint oil and its derivative menthol have been used by humans for thousands of years, the mechanisms by which these compounds induce cold perception remain unclear. About ten years ago, some Transient Receptor Potential (TRP) channels were shown to have important roles in cold perception and cooling sensations induced by cooling agents. In the studies about cold perception, we found that eucalyptol could also cause comfortable cooling sensations on the skin surface without accompanying pain. In addition, the cold perception threshold of cold receptors was found to be easily changeable by ambient temperature.

INTRODUCTION

The ability to process cooling sensations is necessary for living things to survive in cold environments such as regions with harsh winters or the ocean floor. Consistent sensation of cold or cool temperatures is demonstration that this is one of the most important and primitive senses. Temperature sensation plays a role in both comfort and pain. Humans may seek out cooler environments for enhanced comfort, while acute pain sensations help avoid risks that accompany dangerously high or low temperatures. Cold and hot temperature perceptions thus play complementary roles. For cosmetic formulations, cold sensation is a very important property that can be involved in antiperspirant effects, moisture perception, pore shrinkage and lowering of surface temperatures. Indeed, cosmetics containing plant extracts that promote cold perceptio ... ...