Morphological Changes of Human Hair Related to Graying

The study investigated the morphological and mechanical changes in human hair associated with graying. Using both in vitro and in vivo methods, it was found that nonpigmented (gray) hair strands exhibited significantly lower relative amplitude and higher damping performance compared to pigmented hair. This was attributed to increased waviness, larger hair collective volume, higher fiber-fiber interactions, and greater air resistance. The findings highlighted that even small fractions of gray hair (≥5%) significantly impacted the dynamic movement and appearance of hair collectives, affecting the overall perception of hair.