STANFORD, Calif. — Do you ever wonder why your skin feels tight after washing and relieved after moisturizing? A team of scientists at Stanford University has discovered the science behind these sensations. Researchers decoded how physical changes on our skin’s surface translate to what we feel and have presented a method to predict how a person might feel after using various beauty products.
“This work provides a new understanding of how products affect the physical properties of our skin, which includes not just skin health, but also skin sensorial perception. That’s a significant advance,” says Reinhold Dauskardt, the Ruth G. and William K. Bowes Professor in Stanford’s Department of Materials Science and Engineering, in a university release. “It provides a whole new understanding of how to design those formulations.”
The science behind the sensation
Our skin, being the body’s largest organ, interacts continuously with our environment. Its topmost layer, known as the stratum corneum, acts as a protective shield, ensuring moisture retention and preventing harmful elements from entering. When cleansers, especially harsh ones, are applied, they remove some lipids that maintain moisture, causing this layer to shrink. Conversely, moisturizers enhance this layer’s water content, leading it to expand.
Stanford scientists theorized that these physical changes, whether expansion or contraction, trigger mechanoreceptors – sensors converting mechanical force into nerve signals – below our skin’s surface layer. These sensors then send signals to our brain, which we recognize as feelings of skin tightness or relief.
To prove their hypothesis, the team examined the effects of nine moisturizers and six cleansers on skin samples sourced from the cheek, forehead, and abdomen. They observed changes in the stratum corneum and used a detailed skin model to anticipate the signals these mechanoreceptors might send.
Their predictions mirrored the feedback from human trials of these products. In collaboration with L’Oréal Research and Innovation, 2,000 women in France tested the moisturizers, while 700 women in China tested the cleansers. All participants rated their skin tightness feelings post-use.
“We plotted what we were predicting against what human subjects were telling us, and it all fell on a straight line. In other words, we were predicting exactly what they were telling us,” notes Dauskardt. “It was an absolutely remarkable correlation with a very high statistical significance.”
Beyond beauty – The broader applications
This newfound capability to forecast how consumers might feel post-treatment can significantly benefit cosmetic brands. They can refine their product formulations even before human trials. Dauskardt believes this methodology can go beyond merely evaluating skin tightness feelings.
“It provides a framework for the development of new products,” notes Dauskardt. “If you’re doing anything to the outer layer of the skin that’s causing it to change its strain state and its stress state, then we can tell you how that information is transmitted and how it will be understood and reported by consumers.”
Dauskardt envisions utilizing this insight in creating wearable devices. By understanding the brain’s interpretation of skin tension variations, innovative mechanisms for non-verbal, non-visual communication can be developed.
“What we’ve done is reveal how mechanical information gets from the outer stratum corneum layer down to the neurons much lower in the skin layers,” says Dauskardt. “So now, can we communicate through human skin? Can we build a device to provide information to someone non-verbally, non-visually, using our understanding of these mechanisms? That’s one of the areas we’re very interested in.”
The study is published in the journal PNAS Nexus.
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