Age-associated thin hair displays molecular, structural and mechanical characteristic changes

Baltenneck, Frederic; Genty, Gaïanne; Samra, Elias Bou; Richena, Marina; Harland, Duane P.; Clerens, Stefan; Leccia, E.; Balch, Mickael Le; Doucet, J.; Michelet, Jean‐François; Commo, S

doi:10.1016/j.jsb.2022.107908

Cited by 2 publications

(1 citation statement)

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“…Together with the phase of the hair growth cycle, seasonal effects will need to be considered, when investigating the variation of any and, namely, subtle properties for hair samples. These may include a wide range of differences in origin, environmental, and chemical conditions [29,[31][32][33][34][35], the changes of hair properties along its length [9,36], and differences and similarities of individual hairs in a forensic context [37].…”

Section: Discussionmentioning

confidence: 99%

A consumer cross‐over trial suggests that there are significant seasonal changes of the tensile properties (wet) of human hair

Wortmann,

Wortmann

2023

Intern J of Cosmetic Sci

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ObjectivesThrough the cooperation with an industrial partner, we gained a set of data for the tensile properties (wet) of human hair. The hair samples originated from a cross‐over study with two groups of individuals, using for a topical application sequentially two products (A and B). Each phase of the study lasted six months. The phases of the study were by chance covering first largely the winter and then the summer period. Initially, tensile variables were chosen, which not only reflect the mechanical properties of hair (modulus, break strain, break stress) but which are also considered to have a good connection to practice‐relevant hair properties. The initial analysis of the data showed that changes were observed for the variables due to the treatment phases. However, these were either small or difficult to interpret.MethodsAgainst this background and using Two‐Factor Analysis of Variance, we investigated the hypothesis that the tensile properties of hair (wet) may show significant seasonal changes. For this we chose those two independent variables, which reflect the properties of the intermediate filaments (modulus) and the matrix (break strain) in the composite structure of the hair cortex.ResultsThe results support the ‘seasonal’ hypothesis and clearly show that the variables show significant changes from Winter to Summer (modulus: 10% increase, break strain: 3% decrease). The seasonal effect was thus a major reason, why the first stage of the analysis of the data was inconclusive.ConclusionsThe tensile properties of the main morphological components of the cortex show distinct seasonal changes. Towards the summer the hair becomes stiffer and more brittle. Furthermore, the results suggest that seasonal effects may need to be taken into account when conducting studies on lengths of hair grown during different seasons.

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