Hair Hydration Inspired by Skin Care

Hair Hydration Inspired by Skin Care: Way Beyond Water Content!

Abstract

Dry hair requires restoration treatments to recover its hydration and healthy appearance. Hydration in hair is perceived by benefits other than water content. Hydroviton® Hair was then designed to meet the needs of this hair condition, with a film formation activity on the hair fibers that smooths them out, improving combability in wet and dry hair, increasing the perception of softness and alignment, rebalancing electrostatic charges and thus being also effective in controlling volume and frizz.

Introduction

Skin care and hair care are two different universes with different particularities, however, in the last twelve months the terms "care" and "skincare" have been widely seen on social media in hair care-related searches (¹). This data reinforces the concept of "skinification", where ingredients and claims used mostly in skin care are entering the hair universe. A survey conducted by Symrise in 2019 with 50,000 volunteers from 20 countries investigated how consumers understand the hydration attribute. Combability, softness, film formation, frizz and volume control, for example, are factors that add to the perception of hydrated hair, showing that the hair hydration claim implies benefits other than water retention. (²) Ingredients such as polyols (Sorbitol), glycols (Pentylene glycol) and salts of organic acids (Sodium Lactate), for example, are widely recognized for their moisturizing properties in skin care formulations due to their ability to interact with polymeric chains and with water through hydrogen bonds; these interactions make such ingredients capable of acting as film formers and moistening agents. (^{3,4, 5, 6, 7, 8}) Sorbitol is a linear-chain polyhydric alcohol that has 6 hydroxyl groups in its molecular structure, responsible for interacting with water molecules through hydrogen bonds. These interactions favour water/moisture retention in sorbitol structures and explain its hydrating and moistening capabilities in different applications.(^{3, 4, 5, 6, 7, 8}) From the fermentation of sugars occurs the production of lactic acid, which, once neutralized, generates its corresponding salt: sodium lactate, also known to be a hydration promoter, such as sorbitol. (⁹) Due to the presence of these hydroxyl groups, both sodium lactate and sorbitol are recognized as "plasticizing" agents as they intercalate between the polymer chains through intra and intermolecular forces (hydrogenic interactions), increasing flexibility and mobility of formed films. (^7,8,9) Hydroviton® Hair was designed to meet the needs of named dry and dehydrated hair. Bad texture of hair, roughness, excess electrostatic charges (creating volume and frizz), and difficulties in combing are descriptive of this hair condition. In other words, we can classify the product as a hair hydration promoter, according to consumers' perception. The hydration results from the combination of the aforementioned ingredients, in association with Arginine, an amino acid that presents different forms according to specific pH ranges. At the pH of Hydroviton® Hair, Arginine has a net charge equal to +1, indicating that its carboxyl group is deprotonated, while the amino and guanidine groups are positively charged. (¹⁰) Once positive, Arginine favours the anchoring of the film formed by Sorbitol, Lactate and Pentylene Glycol on the hair surface by electrostatic interaction.(^{11, 12, 13, 14}) "Hydration" was the third most popular claim among over 8,000 product launches in hair care in 2021 (¹⁵), which makes Hydroviton® Hair very much in line with the demands of the consumer market. Hydroviton® Hair was applied in standard bases of shampoo and conditioner at 2% and assessed for hair hydration benefits as follows.

Materials and Methods

1) Sensory Panel

The sensory panel is a tool that allows evaluating hair strands treated with different products and/or combinations through the methodology of quantitative descriptive sensory analysis. Unstructured linear scales of 10 cm are used and the product is graded from 1 to 10 and associated with concepts such as "NONE" at one end and "EXTREMELY" at the other. Evaluators mark with a dash the position referring to the concept for each evaluated attribute. The results were submitted to Student's t-testing. References were offered to evaluators at each session. Example of 10 cm unstructured linear scale:

Softness

Forty strands of Caucasian hair (bleached - 5g/25 cm) were previously cleaned with a 10% SLES (Sodium Lauryl Ether Sulfate) solution. The strands were divided into 3 groups: treated with shampoo and conditioner containing 2% Hydroviton® Hair, treated with placebo shampoo and conditioner (hair formulations without the actives) and treated with specific formulations that originated the scale references. The strands of each group were moistened and the formulations were applied as described below: a) Shampoo: 0.5 g per strand; the strands were massaged for 1 minute, rinsed in running water at 33°C and allowed to dry overnight under controlled conditions of humidity and temperature (22 ± 2 °C; 50 ± 5% RH). b) Conditioner: 0.5 g per strand, following the same steps of shampoo application. c) Application process of shampoo and conditioner was repeated 5 times in each strand. Each trained evaluator received a treated strand that was not exposed to the other evaluators in order to avoid influenced perceptions. Evaluated attributes were: softness, volume and frizz control and alignment. Softness: analyzed by comparison with the references. The evaluators massaged and ran their fingers along the entire length of the strands, in order to perceive any differences in softness. Volume Control: analyzed by comparison with references through photo records. The evaluators were trained to compare the body of the strands. Frizz Control: analyzed by comparison with references through photo records. The evaluators were trained to score frizz as the misaligned fibers compared to the others in the body of a strand. Alignment: analyzed by comparison with the references through photo records. The evaluators were trained to score alignment by how convergent and center-oriented the fibers are, therefore aligned in the same direction and angle.

2) Combability Evaluation

The combability test measures the force required by a standard comb to slide through a hair strand. As combing forces are dependent on the interaction between the hair cuticles and the comb, measurements may vary according to the hair's moisture level.  

2.1) Hydroviton® Hair: Improved Combability

Improved combability was evaluated according to the peak force parameter, which represents the maximum force required to comb a hair strand. Five strands of Asian hair per group (5 g, 25 cm, bleached once) were previously cleaned with a 10% SLES solution. Test products were applied five times to each strand (0.5 mL of product + massage for 1 minute, followed by 1 minute of rinsing in running water (33 ± 3 °C, 4 L/min). Wet test was performed using the Dia-Stron MTT 750 testing equipment. Strands were cleaned again with a 10% SLES solution and test products were reapplied in sequence as previously described. Strands were left to dry overnight under controlled conditions of humidity and temperature 22 ± 2 °C; 50 ± 5% RH). Dry test was performed using the same Dia-Stron equipment. The energy involved in the combing of strands was extracted from the measurements performed. Comparisons between treatments were performed with Student's t test with a 95% confidence interval.

Results and Discussion

Sensory Panel

Figure 1 below shows that strands treated with Hydroviton Hair 2% showed an improvement of 8.9% in softness. The film formed on the surface of the fibers contributed to the reduction of irregularities, bringing greater alignment between the cuticles, which made them smoother, even in rinse-off formulations. Figures 2 and 3 below show that the treatment with Hydroviton® Hair resulted in better control of frizz (by 85.3%) and volume (by 60.8%) versus placebo. Treatment with Hydroviton® Hair 2% was also 41.9% more effective than placebo in terms of fiber alignment, as shown in Figure 4 below.

Instrumental Combability Test

As illustrated in Figures 5A and 5B below, Hydroviton ® Hair improved the combability of strands by 14% when wet and by 18% when dry. The results evidenced that the action of Hydroviton® Hair lies in its anchoring on the hair surface, forming a coating film on hair and making cuticles more aligned. The force required to comb the hair is dependent on the interaction between the cuticles and the comb, that is, the easier the slide of the comb between the hair fibers, the lower the energy required to comb them. In addition, by smoothing the surface, the perception of softness is increased, as well as the overall health appearance of hair, with controlled volume and frizz and greater alignment.

Conclusion

The composition of Hydroviton Hair showed good film-forming activity, supported by the presence of positively-charged arginine. At last, the product proved to be very efficient in improving wet and dry combing, in increasing the perception of softness, in taming volume and frizz and in increasing the alignment of the fibers even in rinse-off hair formulations. The combination of these attributes demonstrates Hydroviton Hair's ability to meet consumers' expectations on the hydration of their hair, far beyond the water content of the fibers.   References: (1) Ingefy Atlas, March 2021 – March 2022 vs. (2) Hair Care Demands – Hydration and Nutrition, Symrise CICS Database, 2019. (3) FEATHERSTONE, S., Complete Course in Preservation and Related Processes, Vol. 2, Chapter 8. 14th ed. Woodhead Publishing; 2015. (4) NABORS, LO, Alternative Sweeteners, Chapter 18. 3rd ed. New York: McGraw Decker; 2001. (5) OLIVAS, GI, BARBOSA-CÁNOVAS, GV Alginate-Calcium films: Plasticizer and relative humidity effects on water vapor permeability and mechanical properties. LWT – Food Science and Technology. 2007. (6) SOTHORNVIT R., KROCHTA, JM Plasticizer effect on mechanical properties of β-lactoglobulin films. Journal of Food Engineering 2001; 50: 149-155. (7) LIMA AMF, ANDREANI L., BORSALI R., SOLDI V. Morphology, sound absorption and mechanical properties of films affected by softening and cross-linking process. Quimica NOVA. 2007; 30: 832-837. (8) BALLESTEROS-MARTINEZ L., PÉREZ-CERVERA C., ANDRADE-PIZARRO R. Effect of glycerol and sorbitol concentrations on mechanical, optical and barrier properties of sweet potato starch film. NFS Journal 20, 1-9 (2020). (9) PARRIS N., COFFIN D., JOUBRAN RF, PESSEN H. Composition Factors Affecting Water Vapor Permeability and Tensile Properties of Hydrophilic Films. J. Agric. Food Chem., 43, 1432-1435 (1995). (10) GARRIDO C., AGUAYO T., CLAVIJO E., GOMÉZ-JERIA JS, CAMPOS-VALLETE MM Effect of pH on the Interaction of L-Arginine with Colloidal Silver Nanoparticles. A Raman and SERS Study. J. Raman Spectrosc., 44, 1105-1110 (2013). (11) ROBBINS, CR, Chemical and Physical Behavior of Human Hair, Chapter 1. 4th ed. New York: Springer; 2013. (12) ROBBINS, CR, Chemical and Physical Behavior of Human Hair, Chapter 2. 4th ed. New York: Springer; 2013. (13) ROBBINS, CR, REICH, C., PATEL, A., Adsorption to Keratin Surfaces: Continuum Between a Charge-Driven and Hydrophobically-Driven Process. J. Soc. Cosmet. Chem., 45, 85-94 (1994). (14) SCOTT, GV, ROBBINS, CR, BARNHURST, JD, Sorption of Quaternary Ammonium Surfactants by Human Hair, J. Soc. Cosmet. Chem., 20, 135-152 (1969). (15) Mintel, GNPD – Category Matches: hair care products.   Authors: Rita Cartaxo, Bruna Nakatu, Karolina Lourenço, Rebeca Gasparin, Marcia Paula Symrise AG   Translation and Compilation: Özgür Çelen Turkey Account Manager Symrise AG