Chronological ageing of human hair keratin fibres

Abstract

Examination of very long hair (length > 2.4 m) using a large range of evaluation methods including physical, chemical, biochemical and microscopic techniques has enabled to attain a detailed understanding of natural ageing of human hair keratin fibres. Scrutinizing hair that has undergone little or no oxidative aggression--because of the absence of action of chemical agents such as bleaching or dyeing--from the root to the tip shows the deterioration process, which gradually takes place from the outside to the inside of the hair shaft: first, a progressive abrasion of the cuticle, whilst the cortex structure remains unaltered, is evidenced along a length of roughly 1 m onwards together with constant shine, hydrophobicity and friction characteristics. Further along the fibre, a significant damage to cuticle scales occurs, which correlates well with ceramides and 18-Methyl Eicosanoic Acid (18-MEA) decline, and progressive decrease in keratin-associated protein content. Most physical descriptors of mechanical and optical properties decay significantly. This detailed description of natural ageing of human hair fibres by a fine analysis of hair components and physical parameters in relationship with cosmetic characteristics provides a time-dependent 'damage scale' of human hair, which may help in designing new targeted hair care formulations.

FT-IR Microspectroscopic Imaging of Cross-Sectioned Human Hair during a Bleaching Process

“…The hair was cut into 10-to 15-cm lengths starting approximately 5 cm from the root [20]. Each segment was then embedded in paraffin resin and sliced with a microtome to yield 10-μm-thick cross sections.…”

Hair analysis as a biomonitor for toxicology, disease and health status

“…93 Deterioration obviously will increase as a function of distance away from the scalp, i.e. A particularly interesting publication in this regard is that by Thibaut et al in the rather unique study of hair 2.4 m long that had not been exposed to chemical treatments.…”

Age-Related Hair Pigment Loss

“…These hairs are commonly more pigmented than scalp hair, even at an age when canities is extensive in the latter. There is also evidence from rare 'blocked-in-anagen' case reports [19] in which very long hair fibers representing 3 decades of continuous anagen were similarly pigmented along their entire length. These cases suggest that anagen duration may not be a limiting factor for the maintenance of an optimal pigmentary environment.…”