Human Scalp Hair: Geometry, Biochemistry, Growth Parameters and Mechanical Characteristics
TLDR A 6-group geometric classification of human scalp hair is more reliable and objective for testing than an 8-group system.
The study investigated the reliability of a geometric classification system for human scalp hair, proposing a system with fewer groups for better accuracy. Hair was collected from 128 volunteers and classified into 8 and 6 groups based on geometry, with the 6-group system showing improved reliability (k=0.671) compared to the 8-group system (k=0.418). Curly hair exhibited lower growth rates and tensile strengths, with the straightest hair growing fastest at 0.72 cm/month and the curliest at 0.39 cm/month. No significant correlation was found between hair biochemistry and geometry, although curly hair showed a trend towards higher lipid absorption. A supervised statistical approach using FTIR data improved classification success to 79%, suggesting a more objective method for hair testing in medicine and forensic science. The study supported a geometric classification with fewer groups, highlighting correlations between hair geometry, biochemistry, and physical properties.
