Retinol Has a Skin Dehydrating Effect That Can Be Improved by a Mixture of Water-Soluble Polysaccharides

Passive Enhancement of Retinol Skin Penetration by Jojoba Oil Measured Using the Skin Parallel Artificial Membrane Permeation Assay (Skin-PAMPA): A Pilot Study

Introduction

Retinol is known to have positive benefits on the skin including enhancements in barrier function, increased epidermal thickness, reductions in fine lines and wrinkles and reductions in hyperpigmentation. Improved methods to enhance the penetration of retinol are desirable.

Methods

A study was conducted to examine if addition of natural jojoba (Simmondsia chinensis) oil might help passively enhance the penetration of retinol through the skin's lipid barrier. The model used to examine the passive penetration of the retinol is the skin parallel artificial membrane permeation assay (Skin-PAMPA). In this study, three formulations were examined. The formulations included two control blends: a moisturizing emulsion without retinol and the same product containing 1.0% retinol without jojoba oil. The remaining formulation contained similar concentrations of retinol with 10% jojoba oil. The studies were conducted by applying the products to the Skin-PAMPA models at 37°C/5% CO₂ for 16 hours and then extraction of the acceptor reservoir with cyclohexane (ratio 1:5 acceptor fluid to cyclohexane). The resulting acceptor reservoir cyclohexane solutions were analyzed for retinol by High Performance Liquid Chromatography (HPLC).

Results

The formulations without retinol showed no indications of retinol penetration by HPLC. The control formulation with 1.0% retinol demonstrated that retinol had permeated the membrane in the 16-hour timeframe with a measured Area Under the Curve (AUC) of 7 units. Analysis of the formulation containing 1.0% retinol and 10% jojoba oil indicated retinol had permeated with a AUC of 285 units, a nearly 40-fold increase in active retinol permeation.

Discussion

The ability for jojoba oil to directly act to help skin permeation of a key skin care active like retinol has not been previously demonstrated. This potential for jojoba oil to enhance passive skin penetration of critical skin actives, like retinol, can help to improve the performance of skin care products employing active topical ingredients.

Can Performance and Gentleness Be Reconciled? A Skin Care Approach for Sensitive Skin

People with self-reported sensitive skin may reluctantly use performing anti-ageing skin care products as it could elicit skin discomfort. We thus aimed to design and test an anti-ageing skin care routine that is suitable for people reporting sensitive skin. Key principles for developing products for sensitive skin were applied and formulas were screened for their mildness in vitro using the Reconstructed Human Epidermis ET50 method. Anti-ageing efficacy and mildness was evaluated during a clinical study in China, with 33 female volunteers aged 40–65 years, with sensitive skin. The anti-ageing benefits were measured using Primos 3D, the cutometer and clinical evaluation. Hallmarks for sensitive skin such as skin hydration, skin barrier, skin redness and response to lactic acid were also measured. The ET50 method yielded values suggesting moderate to mild expected irritancy effect in vivo for most of them, and non-irritating effect for the serum. During the clinical study, no physical or functional signs of discomfort were reported with twice-daily usage of the routine. Instrumental evaluation of Wrinkle depth, skin elasticity/firmness, skin hydration, skin barrier and skin redness revealed improvement at 4 and 8 weeks. Clinical evaluation evidenced skin smoothness, skin suppleness and radiance improvements. The skin was less reactive to lactic acid stimuli, while the sensitive skin burden was lowered according to the dermatological quality of life index. Lastly, a separate investigation suggested the potential relief aspect of such routines to alleviate discomforts from mask wearing. With the right formulation design, the benefits of layering products from a routine can be made accessible to people with sensitive skin while simultaneously alleviating the burden of sensitive skin.