Hair Moisturizing Inspired by Skin Care

Hair Moisturization Inspired by Skincare: Well Beyond Water Content! Abstract Dry hair requires restoration treatments to regain its moisture and healthy appearance. Moisture in hair is perceived through different parameters beyond water content. Hydroviton® Hair is a raw material that smooths hair strands, improves wet and dry combing, increases perception of softness and smoothing, rebalances electrostatic charges, and thus demonstrates an effect in controlling volume and frizz.

Introduction

Skincare and hair care are two different universes with distinct characteristics, but over the past twelve months the terms "care" and "skincare" have become prevalent in social media searches related to hair care (1). This data reinforces the concept of "skinification," in which content and claims predominantly used in skincare have entered the hair universe. A survey conducted by Symrise in 2019 with 50,000 volunteers from 20 countries investigated how consumers understand hydration properties. For example, combing, softness, film formation, swelling, and volume control are factors that contribute to the perception of moist hair and demonstrate that hair moisturization claims contain benefits beyond water retention (2). Components such as polyols (sorbitol), glycols (pentylene glycol), and salts of organic acids (sodium lactate) are widely recognized for their moisturizing properties in skincare formulations because of their ability to interact with polymeric chains through hydrogen bonds and with water (3, 4, 5, 6, 7, 8). Through such interactions, these components are capable of acting as film formers and moisturizers (3, 4, 5, 6, 7, 8). Sorbitol is a linear-chain polyhydric alcohol with six hydroxyl groups in its molecular structure, responsible for interacting with water molecules through hydrogen bonds. These interactions support water/moisture retention in sorbitol structures and explain its hydration and moisturization capabilities in different applications (3, 4, 5, 6, 7, 8). From sugar fermentation, lactic acid production occurs, which after neutralization forms the corresponding salt, resulting in sodium lactate, also known as a hydration promoter like sorbitol (9). Due to the presence of these hydroxyl groups, both sodium lactate and sorbitol are considered "plasticizer" substances, as they increase the flexibility and mobility of films formed by entering between polymer chains through intramolecular and intermolecular forces (hydrogen interactions) (7,8,9). Hydroviton® Hair was designed to meet the needs of hair characterized as dry and having lost its moisture. This characterization can be described as poor hair texture, roughness, excessive electrostatic charges (volume and frizz), and difficulties in combing. In other words, according to consumer perception, we can classify the product as a moisture enhancer for hair. Hydration results from a combination of the components mentioned above along with arginine, an amino acid that presents different forms according to specific pH ranges. At the pH of Hydroviton® Hair, the net charge of arginine equals +1, indicating that the proton of the carboxyl group has been removed, while the amino and guanidine groups are positively charged (10). This situation supports the fixation of the film created by arginine, sorbitol, lactate, and pentylene glycol on the hair surface through electrostatic interaction (11, 12, 13, 14). "Moisturization" was the third most popular claim among more than 8,000 hair care product launches in 2021 (15), making Hydroviton® Hair highly aligned with consumer market demands. Hydroviton® Hair was applied at a 2% ratio in standard shampoo and conditioner bases, and its moisturizing properties in hair were evaluated as follows.

Materials and Methods

1) Sensory Panel The sensory panel is a tool that enables the evaluation of hair strands treated with different products and/or combinations through quantitative descriptive sensory analysis methodology. Unstructured linear scales of 10 cm are used, and the product is rated from 1 to 10. One end is associated with concepts such as "NONE" and the other with "EXCESSIVE." Evaluators mark a position with a line referencing the concept for each evaluated property. Results were submitted to Student's t-test, and references were provided to evaluators at each session. Example of 10 cm unstructured linear scale: Softness Forty hair strands (bleached - 5g/25 cm) were previously cleaned with a 10% SLES (sodium lauryl ether sulfate) solution. Hair strands were divided into three groups: one group received shampoo and conditioner containing 2% Hydroviton® Hair; the second group received placebo shampoo and conditioner (hair formulations without active ingredients); the third group received special formulations to establish scale references. Hair strands in each group were moistened and formulations were applied as described below: a) Shampoo: Applied at 0.5 g per hair strand, massaged for 1 minute, rinsed in running water at 33°C, and left to dry overnight under controlled humidity and temperature conditions (22 ± 2°C; 50 ± 5% relative humidity). b) Conditioner: Following the same steps as shampoo application, 0.5 g per hair strand. c) Shampoo and conditioner application was repeated 5 times on each hair strand. Each evaluator also received a hair strand not exposed to application to avoid bias from previous experience. The properties evaluated were: softness, volume, frizz control, and smoothing. Softness: Analyzed by comparison with references. Evaluators massaged and ran their fingers along the entire length of the strands to detect any difference in softness. Volume Control: Analyzed by comparison with references through photographic records. Evaluators were trained to compare the body of the strands. Frizz Control: Analyzed by comparison with references through photographic records. Evaluators were trained to score misaligned strands in a hair bundle body compared to others. Smoothing: Analyzed by comparison with references from photographic records. Evaluators were trained to score alignment based on how convergent and centrally focused the hair strands were, thus aligned in the same direction and angle.

2) Combing Evaluation

The combing test measures the force required for a standard comb to glide along a hair strand. Since combing forces depend on the interaction between hair cuticles and the comb, measurements may vary according to the hair's moisture level. 2.1) Hydroviton® Hair: Improved Combing Evaluated according to the peak force parameter, which represents the maximum force required to comb the hair strand. Five Asian-type hair strands per group (5 g, 25 cm, bleached once) were previously cleaned with a 10% SLES solution. Test products were applied five times to each hair strip (0.5 mL product + 1 minute massage, followed by 1 minute rinsing in running water (33 ± 3°C, 4 L/min). Analysis was performed using a Dia-Stron MTT 750 test apparatus. Strips were cleaned again with a 10% SLES solution and test products were sequentially reapplied as previously described. Strands were left to dry overnight under controlled humidity conditions and 22 ± 2°C temperature (50 ± 5% relative humidity). The dry test was also performed using the same Dia-Stron apparatus. The energy required for combing the strands was determined from the measurements taken. Comparisons between applications were made with Student's t-test at 95% confidence interval.

Results and Discussion

Sensory Panel According to results in Figure 1, strands treated with 2% Hydroviton® Hair showed an 8.9% improvement in softness. It was demonstrated that the film layer formed on the hair strand surface provides smoother hair structure, even in rinse-off formulations.   Figures 2 and 3 show that treatment with Hydroviton® Hair performed better than placebo in controlling frizz (85.3%) and providing volume (60.8%). Application of 2% Hydroviton® Hair was 41.9% more effective than placebo in terms of straight alignment of hair strands, as shown in Figure 4.

Instrumental Combing Test

As shown in Figures 5A and 5B below, Hydroviton® Hair improved combing of hair strands by 14% when wet and 18% when dry. Hydroviton® Hair proved effective in affixing to the hair surface by aligning cuticles more orderly through the formation of a film layer on the hair surface. The force required for combing hair depends on the interaction between cuticles and the comb; that is, the easier the comb glides between hair fibers, the lower the energy required to comb them. Additionally, by smoothing the surface, along with perception of softness, controlled volume and reduced frizz; greater alignment increases the overall healthy appearance of hair.  

Discussion

Hydroviton® Hair's composition demonstrated good film-forming activity supported by the presence of positively charged arginine. Ultimately, the product proved highly effective in improving wet and dry combing, increasing perception of softness, controlling volume and frizz, and increasing alignment of hair strands even in rinse-off hair formulations. All these properties demonstrate Hydroviton® Hair's ability to meet consumer expectations regarding moisture content in hair well beyond water content in hair strands. References (1) Ingefy Atlas, March 2021 – March 2022 vs. (2) Hair Care Claims – Moisturization and Nourishment, Symrise CICS Database, 2019. (3) FEATHERSTONE, S., Complete Course in Preservation and Related Operations, 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 Effect of Plasticizer 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 the process of softening and crosslinking affecting mechanical properties of films. Quimica NOVA. 2007; 30: 832-837. (8) BALLESTEROSMÁRTINEZ L., PÉRUZ-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., Keratin Adsorption to Surfaces: Continuity 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 products. Translator and Compiler Özgür Çelen Turkey Sales Director Symrise AG