From decoding the perception of tightness to a clinical proof of soothing effects derived from natural ingredients in a moisturizer

Abstract

Objective To decode the feeling of skin tightness after application of a cosmetic product and how to soothe this discomfort. To pursue this aim, we considered the ingredient's effect on stratum corneum (SC) biomechanics to differentiate between consumers prone to tightness from those that are not and correlate these effects with mechanoreceptor activation. Methods In vivo clinical trials were used to assess the tightness perception dichotomy between groups of Caucasian women; in vitro experiments were used to measure the mechanical stresses induced in the SC after cleanser and moisturizer application; and in silico simulations were used to illustrate how the measured mechanical stresses in the SC result in the development of strains at the depth of cutaneous mechanoreceptors, triggering tightness perceptual responses. Results Before any cream application, women prone to tightness tend to have a more rigid SC than their less sensitive counterparts, however cleanser application increases SC stiffness in all women. Surprisingly, no correlation was found between tightness perception and hydration measurements by the Corneometer or barrier function, as evaluated by transepidermal water loss. Self‐declared tightness and dryness scores were strongly associated with a self‐described sensitive skin. After application of the optimized moisturizing formula, Osmoskin® containing natural waxes with good filming properties, consumers report a strong decrease in tightness and dryness perception. These results match with laboratory experiments where the cleanser was shown to increase SC drying stresses by 34%, while subsequent application of Osmoskin® decreased stresses by 48%. Finite element modelling, using experimental results as input, elucidates the differences in perception between the two groups of women. It makes clear that Osmoskin® changes the mechanical status of the SC, producing strains in underlying epidermis that activates multiple cutaneous mechano‐receptors at a level correlated with the self‐perceived comfort. Conclusion Integration of the in vivo, in vitro and in silico approaches provides a novel framework for fully understanding how skin tightness sensations form and propagate, and how these sensations can be alleviated through the design of an optimized moisturizer.

The dynamic behavior of skin in response to vibrating touch stimuli affects tactile perception

“…The reason why tactile perception changes with increasing skin deformation remains unknown and should be investigated in the future. Skin mechanical properties (e.g., stiffness ratio or viscoelasticity of each layer) that increase the amount of skin deformation in response to mechanical stimuli may change the tactile stimuli received by the mechanoreceptors 29,43,44 …”

“…Skin mechanical properties (e.g., stiffness ratio or viscoelasticity of each layer) that increase the amount of skin deformation in response to mechanical stimuli may change the tactile stimuli received by the mechanoreceptors. 29,43,44 Small skin deformations during tactile perception may reflect individual differences in the sensory nervous system, leading to interindividual variations in threshold values. The previous section indicated that the magnitude of skin deformation may be related to the subtlety of tactile perception; however, we observed interindividual variations in the stimulus threshold when the peak skin deformations were smaller than 0.36 mm.…”

Reduction of wrinkles: From a computational hypothesis to a clinical, instrumental, and biological proof

“…measured on cheek with Corneometer CM825 Courage & Khazaka). Previous studies demonstrated that formulas containing high concentration of glycerol allowed a strong 19 and long‐lasting 20 moisturizing effect. Therefore, a 20% glycerol in oil/water (O/W) emulsion was applied twice daily on split face versus an O/W emulsion placebo for 4 months.…”

“…measured on cheek with Corneometer CM825 Courage & Khazaka). Previous studies demonstrated that formulas containing high concentration of glycerol allowed a strong 19 and long-lasting 20 (Courage + Khazaka electronic GmbH, Cologne, Germany). For the DTM, which is rather sensitive to the skin superficial layers, the torque applied to the skin was 100 cN cm.…”

Shearing friction behaviour of synthetic polymers compared to a functionalized polysaccharide on biomimetic surfaces: models for the prediction of performance of eco-designed formulations

“…Although a straightforward relationship between subjective consumer tactile perception and a particular ingredient in a formulation is far from being understood, it is well established that low adhesion and friction are desirable physicochemical characteristics. 13,14 Therefore, tools which can be used to fundamentally understand these characteristics will be invaluable to reformulation.…”