We normally associate hair loss, thinning and greying as markers of age, and a new study has now shown how ageing influences the diameter, surface topography, hardness, loss modulus, storage modulus, and tactile perception of human hair.

A further understanding of the different properties of hair and the effects ageing can have can be useful to develop and evaluate better hair products and to advance the understanding of hair biology.

In the study, carried out by the China University of Mining and Technology and published in the Journal of Cosmetic Science , research on the influence of ageing on hair properties was studied to enable a detailed understanding of the natural ageing process.

The studies were carried out on three age group hair samples using a scanning electron microscope (SEM), a TriboIndenter and an artificial finger.

Studying hair

Three characteristic features of tactile perception that could reflect the perceptual dimensions of the fineness, roughness and slipperiness of hair were extracted, and the influences of ageing on the diameter, surface topography, nanomechanical properties, and tactile perception of hair were determined.

The researchers found that in the three age group hair samples, the children's group hair samples have the smallest diameter, and that hair cuticles in the children and young adult groups were relatively complete and less damaged than in the elderly group, showing that surface structure of hair changes with ageing.

The mechanical properties of hair also change with ageing, as the hardness and elastic modulus values of the elderly group hair samples were lower than those of the young adult group samples, indicating that ageing softens the hair surface.

“The damage to the cuticle greatly degrades the mechanical properties of ageing hair. The hardness and elastic modulus values of children's hair are lower than those of adult hair due to the low cysteine, disulphide and fat contents, as well as the fineness of the hair,” says the study.

The research also points to the elastic and viscous moduli of hair changing with cuticle layer, as the elastic properties are dominant compared to the viscous properties at the upper layer, but the latter becomes more obvious as the indent depth increases.

“The tactile perception of hair [also] changes with ageing,” continues the study. “The change in hair tactile perception with age is related to the changes in the hair surface, lipid levels and mechanical properties.”

Further understanding of these effects can lead to better developments in hair biology and for more targeted products, as well as providing dermatologists with several markers of considerable diagnostic importance, say the researchers.

Hair ageing

Hair can play an important role in people's overall physical appearance and self-confidence. Human hair is easily damaged by sun, heating, brushing, bleaching and colouring treatments.

Also, as age increases, hair also begins to change. Compared with the external factors, internal factors such as ageing are less frequently studied.

With ageing, the follicle becomes smaller and produces less melanin. Meanwhile, the oil glands shrink over time and cannot produce oil as efficiently.

These changes will result in split ends, a grey colour, a brittle and coarse texture, and a dull and thin appearance. Greying, thinning, dryness and brittleness are the four main problems of ageing hair.

Cosmetics Design-Europe, (24/03/2016)