Objective To investigate the effects of different molecular weight (MW), wool derived hydrolysed keratins (i.e. peptides) on the physical properties of relaxed textured hair. Methods Very curly hair of African origin was relaxed using sodium hydroxide-based treatment. Relaxed hair was treated with different MW peptides derived from keratin protein and an amino acid, L-Leucine. The low-MW keratin peptides were 221 Da, the mid-MW keratin peptides were approximately 2577 Da, and the high-MW keratin peptides were approximately 75 440 Da. The penetration of these different peptides into relaxed hair was evaluated using a laser scanning micrometre and by fluorescence microscopy. The effect of these compounds on single-fibre mechanical properties and thermal properties was evaluated using tensile and DSC testing, respectively. Results Low- and mid-MW compounds were able to penetrate deep into the hair cortex. High-MW peptide adsorbed onto the hair surface and possibly slightly penetrated into the outer layers of the fibre surface. Both mid- and high-MW keratin peptides, increased Young's modulus and reduced hair breakage at 20% and 80% relative humidity. With the exception of mid-MW peptide, other peptides and amino acid were not able to modify thermal properties of relaxed textured hair. Conclusions Our data suggest that low-MW compounds may increase hair volume, and high-MW peptides may repair damage on freshly relaxed textured hair.

https://onlinelibrary.wiley.com/doi/epdf/10.1111/ics.12663

Penetration of different molecular weight hydrolysed keratins into hair fibres and their effects on the physical properties of textured hair

This article describes the development of a culturally informed hair collection protocol for cortisol research with Black women. We first conducted a formative research study investigating the acceptability of hair cortisol sampling for African-American college women, where acceptance reached 54%. Findings, including the reasons reported for participation, were then used to develop a culturally informed hair sampling protocol for two studies in a community setting where acceptance improved to 75%. Specific barriers to hair sampling for research in this population were supported. Recommendations to increase participation in hair sampling are provided.

Development of a culturally informed protocol for hair cortisol sampling in Black women

O cortex e a regiao intermediaria do fio capilar onde e possivel modificar a forma do cabelo. Nesta regiao encontramos as ligacoes de dissulfeto, as ligacoes ionicas e as de hidrogenio. Essas ligacoes, ao sofrerem uma mudanca em sua conformacao, proporcionam a modificacao necessaria para o alisamento capilar. Atualmente existem duas categorias de alisamento, o temporario, no qual o agente primario necessario e a agua e o calor, e o alisamento permanente, onde sao usados ativos alisantes altamente alcalinos (pH > 9,0) e diferentes mecanismos de acao para modificar a forma do cabelo. Devido a gama de produtos contendo esses ativos alisantes existentes no mercado e a velocidade com que sao lancados novos outros pela industria cosmetica, torna-se importante conhecer esses ativos, bem como seus mecanismos de acao. Esse conhecimento contribui na seguranca e eficacia dos produtos, alem de evitar o uso indiscriminado de substâncias nao autorizadas pelo orgao sanitario, visto que alguns ativos alisantes podem oferecer mais riscos a saude e danos aos fios que outros.

/pdf/substancias-ativas-do-alisamento-capilar-e-seus-mecanismos-1m8cq9l97f.pdf

Substâncias ativas do alisamento capilar e seus mecanismos de ação

Racial Discrimination, Racial Identity Attitudes, and Obesity Among African American Collegiate Women

The environment causes daily damage to the hair shaft that cannot be repaired and is more evident in the distal part of long hair. Clinical signs of hair damage depend on type of damage and severity of damage. The resistance of hair to mechanical, physical, and chemical injuries is reduced in cases of hair diseases.

Clinical Signs of Hair Damage

Surveys indicate that many South African women use relaxers to straighten their hair for cosmetic reasons, which can damage the hair and scalp. The objective of this study was to assess the effects of treating hair with two types of relaxers: Product A (a lye relaxer, sodium hydroxide base) and Product B (a no-lye relaxer, guanidine hydroxide base). Five adult black female South African subjects were used for the study that was divided into two parts. The first part used a half-head study design in a clinical study in which the researcher and the subjects visually assessed various hair quality parameters before and after relaxer treatment. Product B was assessed to perform better (p = 0.032) than Product A in terms of hair straightening. The second part of the study involved hair amino acid analysis by reversed-phase high performance liquid chromatography. There was a decrease in the amount of cystine [Median (range) g/100 g hair] after treatment with both Product A [7.8 (2.5-9.9), p = 0.086] and Product B [4.0 (2.9-4.8), p = 0.005] compared to before treatment [9.1 (6.4-11.9)]; this decrease was greater (p = 0.085) for Product B. Reduction in cystine content was consistent with increased straightness. Product B (the no-lye relaxer) was found to be more effective and safer to use.

Cosmetic and amino acid analysis of the effects of lye and no-lye relaxer treatment on adult black female South African hair

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Cosmetic and amino acid analysis of the effects of lye and no-lye relaxer treatment on adult black female South African hair