Laeticia Cattuzzato, Florence Clemenceau, Sandy Dumont, Alicia Roso, Cécile Taillebois
2013, 22nd IFSCC conference
Introduction
Moisturizing action is one pillar of cosmetic formulas efficiency. Moisturizing is indeed of high importance to maintain healthy skin, irrespective of skin type and age consideration. Moisturizing effect is also a key driver concerning customer satisfaction, as the benefit is quickly perceived and easily visible. Furthermore, it has also been demonstrated that well moisturized skin is also more receptive to other active ingredients. The development of optimized moisturizing performance is also linked to the right choice of the formulation base. However, from a practical and economical point of view, a good moisturizing active ingredient should be efficient in every formula base allowing the formulator to play with versatile textures and targeted sensory profiles. This challenge is especially accurate in the development of formulations according to natural labels with limited choice of active ingredients. The purpose of this study is to investigate the flexible performance of an easy-to-use liquid sugar-based moisturizer, in vivo on very dry skin, in several simple and natural gels or emulsions.
Materials and Methods
- Raw materials and formulas To study the influence of the surfactant, the moisturizer was introduced in a simple natural gel and in O/W emulsions. The gelling agent, used in all the formulas, was an easy-to-disperse Xanthan gum coated with Acacia Senegal gum (Available from SEPPIC). Different glucolipid emulsifying systems were examined in the O/W emulsions with various fatty chain lengths: C16-C18, C14-C22. As a non-natural benchmark, the emulsion was also created with the combination of Steareth-2 and Steareth-21 (Available from B.A.S.F.) and Cetearyl Alcohol. To facilitate the analysis on the vehicle influence, the formulations were conducted with the same fatty phase and the same additives (Ecocert compliant preservatives, fragrance, and buffer). The selected fatty phase was a mixture of two esters coming from vegetable origin: Dicaprylyl Carbonate (Available from B.A.S.F.) and Coco Caprylate/Caprate (Available from SEPPIC) in addition with Sweet Almond Oil. The characteristics, microscope examination and stability of the formulas were followed-up to 3 months at room temperature and 45°C. In addition, the microbial safety and the skin tolerance of all the formulations were confirmed before the clinical evaluation. The control emulsions, without an active were also prepared for comparison.
- Clinical study The short-term stratum corneum hydration was evaluated with a corneometry protocol on a panel of 50 women (mean age of 57.8 years-old), selected with very dry skin (Corneometer® CM 825, Courage & Khazaka – randomized application sites on lower legs (shin). The moisturization level was measured before and 3 hours, 8 hours, 24 and 48 hours after a unique standardized application of 2mg/cm2 on each area. Evolution of the skin surface was also followed with dermatoscopy (System Canon EOS 5D Mark II, Canon, associated to DermLiteTM Foto, 3Gen LLC - dermatoscopic images blinded ranked by six trained raters).
Summary of the results
Comparison before and after treatment Looking at the effect as a function of time, compared to the same zone before treatment, all the formulas demonstrate a moisturizing effect. On one hand, for the control emulsions, without an active, the improvement lasts more or less depending on the formula composition: all the formulas show, at least, significant improvement up to eight hours. On the other hand, all the formulas containing the moisturizing active reveal a longer lasting effect, significant up to twenty four hours. Comparison to the non-treated zone The comparisons of the effect to the non treated zone, at the same measurement time, confirm the diverse efficacy of the control emulsions as a function of time. It also confirms without a doubt, the efficacy of all the formulas containing the active ingredient, both gels and emulsions. - Comparison to the control formula The three emulsions containing the active show significant improvement compared to their corresponding control. The moisturizing effect is significantly higher up to twenty four hours for the emulsions with the natural glucolipid emulsifiers and significantly higher up to eight hours for the non natural benchmark. The comparison of the two types of vehicles (gel and emulsion) containing the active demonstrate similar efficacy of the gel and the emulsion with the non natural benchmark. The emulsions with glucolipid emulsifiers demonstrate significant improvement at one point: eight hours for the one based on C16-C18 fatty chain and twenty four hours for the one based on the C14-C22 fatty chain. - Dermatoscopy The dermatoscopic images show a significant reduction of squames compared to the initial skin state, up to twenty four hours after application, for all the formulations. This result is consistent with the common emollient fatty phase for all the formulas. Besides the importance on texture and skin feel, it well demonstrates the interest of the “non-active” ingredients to quickly obtain visible benefits. However, despite the fact that the corneometry measurements show no significant improvements two days after application, three of the four formulas containing the moisturizing active still exhibit significant squames reduction whereas the corresponding controls without an active had no further effect.
Conclusion
In addition to the biological knowledge and understanding of the mode of action, such in use conditions studies provide simple and essential information for the formulator. The results demonstrate the versatile moisturizing effect of the sugar-based active in emulsions as well as in gel. However, the emulsifier structure seems to influence the moisturizing kinetics of the active ingredient. This clinical study also reveals that the moisturizing performance achieved with the natural formulations is at least equivalent to the non natural base. As an interesting perspective, the versatility of the moisturizing effect can be further investigated over a longer evaluation period, after repeated applications and using more innovative and precise investigation techniques such as Raman spectroscopy.
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