a Caucasian hair was obtained from Fesnoux-Sécher, Paris.
b African-American hair was obtained from DeMeo Brothers, Inc., New York.
c Labeling and separation were conducted by Deutsches Wollforschungsinstitut (DWI), Aachen, Germany.
d The TCS-SP2 fluorescence laser scanning confocal microscope is manufactured by LEICA Microsystèmes, Nanterre, France.
e Gluadin WLM (INCI: Hydrolyzed Wheat Protein) is a product of Cognis.
f The Tissue-Tek brand automated slide stainer and coverslipper is a device of Sakura Tinetek Europe, Zoeterwoude, Netherlands.