Elemental Distribution in the Ultrastructure of the Cuticle and Effect on Permanent Hair Color from Metal Ions

Abstract

Hair damage generally increases from root to tip, and exogenous metals easily accumulate on damaged hair from such sources as water. There is a problem that the dyeing property of permanent hair color (oxidative hair dye) has an influence on the hair damage level. 2D elemental distributions and line profiles of the ultrastructure in cuticle layers were observed with a scanning transmission electron microscope equipped with energy dispersive X-ray spectrometry. It was confirmed that copper accumulated in the outermost A-layer and each endocuticle. Not only the cortex but also cuticle layers were dyed with permanent hair color. Hydrogen peroxide is contained in the permanent hair color as an oxidant, and its catalytic effect becomes stronger in the cuticle layers of the damaged part of the hair. As a result, it was considered that the dyeing property was also intensified in the damaged hair part due to the change of the reactivity of the oxidative dyes. It was also confirmed that copper in the outermost A-layer was reduced with chelating treatment, which suggests over-dyeing was suppressed.