Study shows how ethnic hair products need to be formulated differently to be adequate

In the study, carried out by the Advanced Chemical Institute of Catalonia (IQAC-CSIC) and published in the International Journal of Cosmetic Science​, ethnic hairs were assessed related to their lipid composition, and some differences between them were found in terms of water uptake and mechanical properties.

The results of this research have particular relevance to chemists and new product development specialists who work in the ethnic hair-care market.

The research team says that it is clear that African hair differs from Caucasian in a number of important ways, suggesting that the products formulated for Caucasian hair and sold in the general market may not adequately address the special hair-care needs of the African American consumer.

The study opens new prospects for the development of lipid-related products able to increase protection of ethnic hair.

Hair composition​

In the past, biochemical studies have mainly focused on the composition of hair. African hair exhibited lower moisturisation and less radial swelling when flushing with water compared with Asian or Caucasian hair, and they assumed a possible lipid differentiation among human populations.

This study consisted in the lipid characterization of different ethnic hairs (Caucasian, Asian and African hairs) and the influence of these lipids in different hair properties such as humidity and mechanical properties.

Evaluation of water sorption and desorption of the different ethnic hairs and with and without lipids was also studied mainly to determine permeation changes of the keratin fibres.

To carry out the research, extractions of exogenous and endogenous lipids with different organic solvents were performed; lipid analysis and its quantification using thin-layer chromatography coupled to an automated flame ionization detector (TLC/FID) were performed.

Absorption and desorption curves were obtained in a thermogravimetric balance equipped with a controlled humidity chamber, the Q5000SA Sorption Analyzer.

Breaking stress and elongation were also analysed using a computer programmable dynamometer.

Findings​

The team found that the highest amount of total lipids were extracted from the African hair, which may come from external sebaceous lipids.

Caucasian fibres were found to be the most hydrated fibre, and a decrease in moisture was found in the extracted fibres; while a superior lineal mass was found for the Asian fibres which supported their higher strength.

The results obtained from the analysis of the mechanical properties of delipidized fibres indicate a surprising increase in the strength of African and Caucasian fibres, which the scientists say could be related to the humidity decrease in lipid-extracted hair fibres.

Results of water uptake and desorption indicate that Asian and Caucasian hairs present the lower diffusion coefficients compared with the African ones.