Engineering Cosmetics to Combat Skin Stress and Promote Skin Comfort
Podium 31
Presented by: Reinhold Dauskardt
Introduction: The formulation of performant cleansers and moisturizers should include their effects on the consumers sensorial perception of skin comfort. However, the connection between such subjective “feel-good” factors and the effect of the skin care formulation on salient neural activity including the activation of mechanoreceptors beneath the skin surface are only recently being revealed. In particular, the important role of skin stress on activating such neural activity provides a critical quantitative link between the skin care product and the perception of skin comfort. Exploiting this link provides a powerful tool to engineer improved cosmetic formulations that combat skin stress and enhance consumer skin comfort for extended durations after application.
The biomechanical response of the stratum corneum (SC) to cleansers and moisturizers is central to combatting skin stress and downregulating neural activity for improved skin comfort. If not properly formulated, cleansers result in an increased skin stress through excessive drying of the SC which can be quantitatively linked to the activation of mechanoreceptors and the perception of skin tightness. Similarly, while moisturizers provide improved SC hydration, they can be engineered to further combat skin stress over extended times for enhanced skin comfort. In both cases, the biomechanical response of the SC to skin care formulations can be quantitatively measured with ex vivo models and used in predictive computational models of consumer skin comfort.
In this work, ex vivo SC models were used to fully characterize the changes in skin stresses resulting from the application of selected cleanser and moisturizer formulations. In conjunction, quantitative computational models of the mechanical response of the underlying skin layers and the activation of mechanoreceptors were used. The resulting predicted neural activity unveils the link between the skin care formulation and the consumer neuro-perception of skin comfort.
Methods: Selected cleansers and moisturizers were evaluated using consumers evaluation studies of several thousand women in two countries over successive years. Respondents used the products for a week to assess their effect on skin comfort over a daily time and from this a comfort score was obtained for each product. We evaluated also in a clinical protocol the soothing effect of the best moisturizer after the aggression triggered by a harsh cleanser. The same cosmetic treatments were tested in laboratory in vivo SC models to measure the evolution of skin stress over a period of 10-15 hours after application of the treatment. For each product, the corresponding measured SC properties informed computational finite element models of skin sections with realistic topography based on skin section images. The model predicted the mechanical deformation of underlying skin layers at depths where mechanoreceptors and the neurons that innervate them are located. The results of these simulations were used as inputs to numerical models of neural activity, which predict neural signaling that results from each of the cosmetic products.
Results: From skin comfort scores in consumers responses, two groups of cleansers became distinguishable (mild and harsh), while three groups of moisturizers were identified (low performing, mid performing, and high performing). A strong linear trend between the reported skin comfort scores and the SC drying stresses measured in the laboratory was observed. Beyond this, a similar linear trend was found between modeled neural activity and skin comfort scores. The soothing mechanism of the best moisturizer after the barrier aggression with a harsh cleanser was also validated.
Discussion/Conclusion: The results from consumer evaluation studies of the perception of skin comfort, ex vivo laboratory measurements and numerical simulations were found to provide a consistent and robust description of the performance of cosmetic treatments. Measured skin stress involving the response of the SC to cleanser and moisturizer formulations are useful predictors of skin comfort. The connection is validated by finite element computational simulations of skin sections and numerical models of neural activity that show how skin stress translates to a nervous system response. Results from this study provide a more quantitative process for engineering cosmetic products to include wellness factors such as skin comfort. Additionally, studies combining clinical and consumer evaluation studies with laboratory and computational data are an avenue to new findings in the field of emotional perception and well-being.
The biomechanical response of the stratum corneum (SC) to cleansers and moisturizers is central to combatting skin stress and downregulating neural activity for improved skin comfort. If not properly formulated, cleansers result in an increased skin stress through excessive drying of the SC which can be quantitatively linked to the activation of mechanoreceptors and the perception of skin tightness. Similarly, while moisturizers provide improved SC hydration, they can be engineered to further combat skin stress over extended times for enhanced skin comfort. In both cases, the biomechanical response of the SC to skin care formulations can be quantitatively measured with ex vivo models and used in predictive computational models of consumer skin comfort.
In this work, ex vivo SC models were used to fully characterize the changes in skin stresses resulting from the application of selected cleanser and moisturizer formulations. In conjunction, quantitative computational models of the mechanical response of the underlying skin layers and the activation of mechanoreceptors were used. The resulting predicted neural activity unveils the link between the skin care formulation and the consumer neuro-perception of skin comfort.
Methods: Selected cleansers and moisturizers were evaluated using consumers evaluation studies of several thousand women in two countries over successive years. Respondents used the products for a week to assess their effect on skin comfort over a daily time and from this a comfort score was obtained for each product. We evaluated also in a clinical protocol the soothing effect of the best moisturizer after the aggression triggered by a harsh cleanser. The same cosmetic treatments were tested in laboratory in vivo SC models to measure the evolution of skin stress over a period of 10-15 hours after application of the treatment. For each product, the corresponding measured SC properties informed computational finite element models of skin sections with realistic topography based on skin section images. The model predicted the mechanical deformation of underlying skin layers at depths where mechanoreceptors and the neurons that innervate them are located. The results of these simulations were used as inputs to numerical models of neural activity, which predict neural signaling that results from each of the cosmetic products.
Results: From skin comfort scores in consumers responses, two groups of cleansers became distinguishable (mild and harsh), while three groups of moisturizers were identified (low performing, mid performing, and high performing). A strong linear trend between the reported skin comfort scores and the SC drying stresses measured in the laboratory was observed. Beyond this, a similar linear trend was found between modeled neural activity and skin comfort scores. The soothing mechanism of the best moisturizer after the barrier aggression with a harsh cleanser was also validated.
Discussion/Conclusion: The results from consumer evaluation studies of the perception of skin comfort, ex vivo laboratory measurements and numerical simulations were found to provide a consistent and robust description of the performance of cosmetic treatments. Measured skin stress involving the response of the SC to cleanser and moisturizer formulations are useful predictors of skin comfort. The connection is validated by finite element computational simulations of skin sections and numerical models of neural activity that show how skin stress translates to a nervous system response. Results from this study provide a more quantitative process for engineering cosmetic products to include wellness factors such as skin comfort. Additionally, studies combining clinical and consumer evaluation studies with laboratory and computational data are an avenue to new findings in the field of emotional perception and well-being.