Infrared assessment of human facial temperature in the presence and absence of common cosmetics

Kaikai Zheng; Ruoyu Dong; Huan Wang; Steve Granick

(1) Cosmetics that lower skin temperature by the physical principle of evaporative cooling. The fact that liquids absorb heat to evaporate has been used for thousands of years for air conditioning, at least as long ago as in ancient Egypt, Persia, and India. 11 In cosmetics, this short-term effect appears to disappear after 5-15 min. (2) Cosmetics that lower skin temperature by acting as a barrier layer between skin and surrounding air. The effect is marked for creams but the effect appears to disappear after 20-30 min, perhaps as cream is absorbed into the skin. (3) Cosmetics that lower skin temperature because they contain solids. The effect was most marked for brightening cream and powder highlighter, cosmetics #1 and #3, respectively. Depression of skin temperature appears to persist semi-indefinitely, probably because solid particles in the cosmetic, with lower emissivity than skin, are embedded in the skin. However, this effect is less prominent for foundation (cosmetic #6), suggesting that size of the solid particles matters.