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The skin performs a variety of physiological functions, including protecting the body and regulating its temperature, playing an important role in maintaining homeostasis. Keeping the skin clean is important to the effectiveness of these functions, but excessive washing can remove too much sebum, causing dryness and diminishing the skin’s barrier function. Ensuring a diverse and well-balanced microbiota population on the skin is also important to maximizing the skin’s natural power. Skin cleansers should thus ideally provide selective washing—removing what the skin doesn’t need while leaving behind what it does.
The surfactants used in skin cleansers are typically either fatty acid salts or polyoxyethylene alkyl ether sulphate (AES) (Table 1). Lion uses fatty acid salts because they leave the skin feeling clean and refreshed.
Table 1
Surfactants Commonly Used in Body Washes and Hand Soaps
The fatty acid salts used as the cleaning agents in skin cleansers not only remove grime, but have a broad antibacterial effect. As shown in Figure 1, the fatty acid salts C12K and C14K exhibit a bactericidal effect on E. coli bacteria, whereas AES (labeled C12AE2S) exhibits almost no such effect.
An emulsion of E. coli was mixed with a surfactant solution. At 0, 10, 20, 30 and 60 seconds after mixing, the resulting mixture was applied to a culture medium. After being cultured for 24-hours, the bacteria colonies growing in the medium were counted, and the bactericidal efficiency of each surfactant was calculated using the following formula: Bactericidal efficacy = log(initial bacteria count/remaining bacteria count).
In addition, fatty acid salts have an inactivation effect on viruses. As shown in Figure 2, fatty acid salt surfactants have a higher inactivation effect than AES on feline coronavirus. 2 Studies have also found that fatty acid salt surfactants have a greater inactivation effect on influenza virus than AES. 3, 4
A fluid containing active virus was mixed with a surfactant solution (40 mM) and allowed to react for 5 minutes. The mixture was then used to inoculate cell cultures, and the concentration at which 50% of the cells were infected (the titer, TCID50) was measured.
However, fatty acid salt-based skin cleansers have been found to not kill beneficial Staphylococcus epidermidis bacteria on the skin (Lion data). Furthermore, calcium palmitate, a type of fatty acid salt, has been found to efficiently kill pathogenic Staphylococcus aureus and Cutibacterium acnes, while displaying little sterilizing effect on Staphylococcus epidermidis , thus demonstrating selective sterilization.5 Fatty acid salts may be useful as surfactants that act selectively, sterilizing pathogens, such as E. coli, Staphylococcus aureus and viruses, while leaving intact the ordinary components of skin flora like Staphylococcus epidermidis that play an important role in skin health.
References
Leveraging the advantages of fatty acid salts, Lion has developed skin cleansers with a strong moisturizing effect. Such development both answers the call of many customers for moisturizing effects and enhances the natural power of the skin, for which moisture is crucial.
Cleansing products formulated with moisturizers have been around for a long time, but usually most of the moisturizing ingredients wash away during use. To solve this problem, Lion developed a new skin cleansing agent in which the moisturizing ingredient converts from a hydrophilic to hydrophobic substance when diluted with water during use. A phenomenon called coacervation that occurs when a detergent is diluted with water creates hydrophobic complexes of moisturizing ingredients. These moisturizer complexes firmly adsorb to the skin, creating a coating that does not wash away, thereby providing effective moisturizing.
Lion’s R&D has thus created a new type of cleanser that effectively washes away grime while selectively leaving behind necessary moisture.
To maximize the skin’s natural power, other approaches, besides washing, are also necessary. For example, Lion also focuses on skin care that works from within the body.
In its sleep research, Lion found that ingesting sake yeast improves sleep quality. Good sleep encourages the secretion of growth hormones that are crucial for the maintenance and improvement of health and has been found to increase the density of collagen in the cheeks (Figure 3), suggesting efficacy in improving skin elasticity and texture.
For five weeks, a treatment group of 10 individuals ingested tablets containing sake yeast before bed, and a control group of nine individuals ingested placebo tablets containing no sake yeast before bed. Their cheeks were then assessed by means of ultrasound imaging analysis using DermaScan® (made by Cortex Technology).
Lion’s ability to take these varied approaches is thanks to its unique, diverse range of businesses, from household products to foods with function claims and OTC drugs. Working not only from outside the body, but from within as well, Lion will continue to offer products that help maintain the natural health of the skin and contribute to mental and physical health.
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