A relationship between the use of UV protection and melanin pigmentation identified from changes in individual facial images over 12 years

Abstract

Is it feasible that the chemicals present in the natural dyes and colours of both plants and insects, which in the past have been exploited for their colour, could exhibit other properties that in the future will be understood and exploited for the health and wellbeing of mankind? The melanin component of skin pigmentation in the face greatly affects perceived age. In this study, we have analysed individual differences in how the melanin component changes with time. We consider the frequency of use of ultraviolet light (UV) protection as a factor causing individual difference in aging. It is known that melanin is produced in human skin in response to exposure to UV, which promotes aging effects such as darkening and unevenness of skin colour. In our previous work, we applied principal component analysis (PCA) to the distribution of facial skin colour and obtained feature values that quantitatively describe it. By changing these feature values, we simulated the appearance of a human face of arbitrary age. Accordingly, we found that the melanin component around the cheeks especially tends to increase with age. However, only the averaged feature values were used for each age in this analysis. In the present study, we take the next step of considering individual differences. We constructed a database of facial images taken in 2003 and 2015, including 60 subjects photographed in both years. Subjects’ frequency of UV protection use was also recorded. By applying the same analysis as our previous study, we obtained PCA scores that describe the changes in individuals’ faces from 2003 and 2015. From trends in these data, we found that people can brighten their whole face after 12 years if they use UV protection throughout the year.