Characterization of facial skin of various Asian populations through visual and non-invasive instrumental evaluations: influence of seasons.

BACKGROUND/PURPOSE: This multicenter study assessed the impact of two types of extreme seasons (i.e. summer and winter) on the facial skin of female subjects living in different regions of Asia. METHODS: Facial skin of female subjects of various Asian ethnicities was characterized during summer and winter using dermatological assessments of the cheek and instrumental evaluations of the forehead and cheek. Approximately, 100 female subjects each from five cities in Asia (Harbin and Shanghai in China; New Delhi, India; Seoul, South Korea; and Sendai, Japan) ranging in age from 14 to 75 years were included in this study. RESULTS: Dermatologist assessments revealed a general decrease in severity of roughness, wrinkles, pigmentation, and lentigines during winter compared with summer. Instrumental assessments revealed significant differences in various parameters in winter vs. summer such as reductions in melanin index and skin surface hydration, and increases in transepidermal water loss, skin pH, redness, and sebum production. CONCLUSION: Facial skin in female subjects living in different Asian cities exhibited a wide range of changes and worsening of various biophysical parameters in response to the low temperature and humidity during the winter season as compared with summer.

Facial skin fluorescence as a marker of the skin's response to chronic environmental insults and its dependence on age.

BACKGROUND: Throughout life facial skin is exposed to a variety of adverse environmental conditions and is constantly required to repair itself. The rate of epidermal cell proliferation is indicative of the skin's repair rate and can be monitored noninvasively in vivo using skin intrinsic fluorescence markers. OBJECTIVES: The goal of the present study was to assess the effects of ageing, geographical region, ethnic origin and season on the ability of facial skin to repair itself in the presence of chronic environmental insults using in vivo fluorescence spectroscopy. METHODS: Skin fluorescence emission was measured on the cheeks of 522 individuals in winter and repeated in summer in five different geographical locations in the Asia-Pacific region. Fluorescence emission was also measured from 80 caucasians of fair complexion in the United States (New Jersey area) on the face and on a relatively protected area (upper inner arm). The age range of the participants was 14-75 years. RESULTS: We found that epidermal proliferation rates decrease monotonically with age, while the fluorescence of collagen and elastin cross-links increases with age indicating accumulation of advanced glycation end-products. These trends were independent of geographical region, ethnic origin and season of measurement. Epidermal proliferation rates of facial skin were higher than those of unexposed sites; they may be 10 times higher in younger (second decade) than in older (seventh decade) individuals, and they decrease with age at rates 10 times faster compared with those of unexposed sites. CONCLUSIONS: This is the first time that epidermal proliferation and its dependence on ageing have been measured noninvasively on the human face. The higher tryptophan fluorescence values on the face vs. the protected site are indicative of accelerated rates of epidermal proliferation in the presence of chronic environmental insults. The repair potential of facial skin, i.e. its ability to maintain high proliferation rates, is maximal in younger populations and gradually decreases with age.