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

Kaikai Zheng; Ruoyu Dong; Huan Wang; Steve Granick

is the (which was not peer-reviewed) The copyright holder for this preprint . Raw data. Fig. 1 illustrates raw data. The left panel (Fig. 1a) , a typical thermal image, shows skin temperature measured in different regions of the subject's face. One complication is that the subject inevitably shifted position of his head during the long measurement times, thereby presenting the possibility that the apparent temperature might shift owing to change in the measurement focus. To compensate for this possibility, we made differential measurements between two regions of the forehead, one blank region (cosmetic-free), one region to which cosmetics were applied. Showing the excellent reproducibility of the measurement over extended times, Fig. 1b illustrates apparent absolute temperature plotted against time. Naturally, this healthy subject's skin temperature of ≈ 34.35 C was below his body temperature, which was normal. Creams, powder. In Fig. 2 , the effect of applying cosmetic is considered. Depression of skin temperature is plotted against time after the cosmetic was applied. Cosmetic #1, marketed as a tone-up brightening cream, produced the largest depression of skin temperature. Skin temperature was depressed by at least 2 C for 15 min and 1 C for 20 min, likely because evaporation of volatile components lowers temperature. The evaporation rate was notably slow, perhaps because the volatile components (water) also dissolve in the skin. After the cosmetic had remained on the skin for 40 min, it was washed with cosmetic remover and strikingly, the skin temperature remained depressed by ≈ 0.8 C. This semi-permanent depression of skin temperature likely reflects the presence of residual solid-state brightener specified as an active ingredient in the product's marketing.