Evidence for Calcium Soaps in Human Hair Shaft Revealed by Sub-Micrometer X-Ray Fluorescence

The study revealed the presence of calcium in human scalp hair shafts using X-ray microfluorescence imaging. It identified two types of calcium: one that could be easily removed by hydrochloric acid, found in the cortex, cuticle, and medulla core, identified as calcium soaps; and another type that was not easily removable, located in the medulla wall, cuticle, and cortex, possibly involved in Ca2+-binding proteins. The concentration of the latter type was consistent across different individuals.