Image based quantification method reveals differential patterns of lip desquamation associated with age and sex

The rough surface of lip skin is a dermatological and aesthetic issue that affects facial appearance. While several studies have addressed this common problem, none of them have exclusively utilized image analysis techniques. In this study, we aimed to quantify lip desquamation from facial images in a total of 55 participants and compare the results to those obtained from the tape-stripping method. The central region of the lower lip was extracted from each facial image, and global thresholding was applied using the threshold value T, which is defined as Mean + 2.5 SD. In this equation, Mean and SD represent the average and standard deviation of each grayscale values within the image, respectively. The desquamation rate was calculated as the proportion of pixels corresponding to desquamated flakes within the analyzed region. We found that our approach accurately represented the lip surface states, with a strong correlation with visual assessment (VA) scores (r = 0.715, p < 0.001). To investigate the relationship between lip desquamation and age, we further analyzed the facial images of 1,000 individuals. A gradual decline in lip desquamation with age was observed in males (r = -0.151, p < 0.001) and females over 38 years (r = -0.133, p < 0.05). In contrast, the variation of lip desquamation among females under the age of 38 showed an increasing trend (r = 0.234, p < 0.01). It is notable that the most pronounced differences between sexes were only observed in individuals in their 20s (p < 0.001). Such results imply that the characteristics of epithelial layer of lip can be segmented based on chronological age and sex. These notable changes in lip desquamation were discovered for the first time in this study. Given the current ease of acquiring image data, our image-based method has the potential to advance the lip skin research.