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. 2022 Nov-Dec;14(6):197-203.
doi: 10.4103/ijt.ijt_158_20. Epub 2023 Jan 31.

Impact of Acid ("Progressive Brush") and Alkaline Straightening on the Hair Fiber: Differential Effects on the Cuticle and Cortex Properties

Maria Valéria Robles Velasco  1 , Tânia Cristina de Sá-Dias  1 , Michelli Ferrera Dario  1 , Valcinir Bedin  2 , Marjory Bernardes Fileto  1 , Andressa Costa de Oliveira  1 , Claudinéia Aparecida Sales de Oliveira Pinto  1 , André Rolim Baby  1
Affiliations

Impact of Acid ("Progressive Brush") and Alkaline Straightening on the Hair Fiber: Differential Effects on the Cuticle and Cortex Properties

Maria Valéria Robles Velasco et al. Int J Trichology. 2022 Nov-Dec.

Abstract

Background: Glyoxylic acid has emerged as a safe alternative to formol (formaldehyde) use as a hair straightener/relaxer. However, the possible damage to the hair fiber after its application is low known and/or published in the literature.

Aims: This work aims to characterize hair locks treated with glyoxylic acid compared to traditional alkaline straighteners such as sodium and guanidine hydroxide and ammonium thioglycolate.

Materials and methods: The morphology of the hair cuticles was observed by scanning electron microscopy. Protein loss was assessed by the Lowry method modified by Peterson and as mechanical properties that were expressed in terms of tensile strength.

Results: All products (sodium and guanidine hydroxides and ammonium thioglycolate) caused protein loss of about 2.5 μg/g, except glyoxylic acid that caused the worst damage (3.5 μg/g), in relation to the untreated (virgin) hair (1.12 μg/g), indicating that the chemical treatments can cause hair damage in both cuticles and cortex. The force to break the fibers treated with traditional straighteners based on sodium hydroxide, guanidine hydroxide, and ammonium thioglycolate was statistically the same.

Conclusion: The treatment with glyoxylic acid showed rupture tensile statistically equivalent to the alkaline straighteners. The mechanism of action of glyoxylic acid does not appear to be based on breaking and rearrangement of disulfide bridges, but altered them, that influenced the hair strength. However, it is also essential to consider other factors relevant: technical application technique, reaction time, and interval of reapplication of the product, as this can change the pattern of the results obtained.

Keywords: Acid and alkaline; damage; hair; protein loss; straightener.

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Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
Protein loss (as albumin equivalent) of hair tresses treated with different straightening products. Means that do not share a letter are significantly different (α = 0.05)
Figure 2
Figure 2
Tension at break of hair tresses treated with various straightening products. Means that do not share a letter are significantly different (α = 0.05).
Figure 3
Figure 3
Cuticle morphology of relaxed hair. (a) virgin hair; (b) guanidine hydroxide; (c) sodium hydroxide; (d) ammonium thioglycolate; (e) glyoxylic acid
See this image and copyright information in PMC

References

    1. Goshiyama AM. Masters Dissertation. University of São Paulo: Faculty of Pharmaceuticals Sciences; 2019. Evaluation of hair fibers properties treated with acid straightener at different pH values.
    1. Lai-cheong JE, Mcgrath JA. Structure and function of skin, hair and nails. Med. 2013;41:317–20.
    1. Villa AL, Aragão MR, Santos EP, Mazotto AM, Zingali RB, Souza EP, et al. Feather keratin hydrolysates obtained from micro-bial keratinases: Effect on hair fiber. BMC Biotechnol. 2013;13:15. - PMC - PubMed
    1. Ferreira LA, Braga DC. Active substances of capillary straightening and their action mechanisms. Ele J Pharm. 2016;8:56–6.
    1. Sá-dias TC. Doctoral Thesis. São Paulo: Faculty of Pharmaceutical Sciences of University of São Paulo; 2015. In vitro Evaluation of the Effect of Different Chemical/Thermal Straightening Processes on Hair Fiber.