TAGS: Skin Care
Kao Corporation’s Skin Care Products Research Laboratory, Material Science Research Laboratory, Analytical Science Research Laboratory and Biological Science Research Laboratory have discovered that the unsaturated fatty acids*1 contained in secreted sebum have a negative effect on the skin barrier function that can cause dryness.
New Technology that Utilizes Hydroxypropyl Cellulose (HPC)
By successfully developing a new technology that utilizes hydroxypropyl cellulose (HPC) which forms a sponge-like structure and selectively combines with unsaturated fatty acids to trap them on the skin. Kao expects to be able to suppress contact between unsaturated fatty acids and skin with this technology.
The findings were presented at two events. They were the 48
th Convention of the Japanese Cosmetic Science Society (June 23–24, 2023 in Tokyo) and the 74
th Divisional Meeting of Division of Colloid and Surface Chemistry (September 12–15, 2023 in Nagano).
While sebum secreted from our skin works as a moisturizer to protect it from dryness. A survey on skin problems revealed that about 40% of people with oily skin feel dryness in the winter after washing their face. This matches the response of people with dry skin
*2.
This prompted Kao to examine the correlation between skin surface sebum and skin functions to understand the effects of sebum on skin conditions.
In May 2021, Kao collected skin surface sebum from the right cheeks of 125 men and women of 25-45 ages, at 90 minutes after face washing, they measured trans-epidermal water loss (TEWL), an indicator of skin barrier function. They also measured water content in the stratum corneum. They did this to examine the correlation.
Quantity and Quality of Sebum Can Affect Skin Barrier Function
Subjects were divided into two groups according to the amount of sebum secretion
*3. Results showed that in the group with 5μg/cm
2 or greater sebum secretion, a lower skin barrier function was clearly associated with lower water content in the stratum corneum. Furthermore, qualitative analysis of sebum components confirmed a correlation between a higher ratio of unsaturated fatty acid rate in sebum and lower skin barrier function.
This suggested that in subjects with 5μg/cm
2 or greater sebum secretion, a high ratio of unsaturated fatty acids may lead to both a lower skin barrier function and less water content in the stratum corneum. The group of subjects with less sebum secretion did not show such a correlation.
The above results suggest that it is not only the quantity of sebum but also the quality (ratio of unsaturated fatty acids) that influences skin barrier function and can have a negative influence on the skin by lowering the water content in the stratum corneum. These were clarified for the first time through this research.
These findings prompted Kao to explore ways to reduce unsaturated fatty acids. These acids can cause negative effects on the skin while maintaining the hydrating function of sebum. This led to the development of a technology that selectively gels and traps unsaturated fatty acids. The research involved mixing individual components contained in sebum with a wide range of polymers to see whether they gelled. It was found that a certain type of HPC immediately and selectively gelled oleic acid (OA), an unsaturated fatty acid.
Furthermore, it was also discovered that when HPC was processed to easily dissolve in water, it was effective in gelling and trapping more OA.
Further analysis was conducted to clarify the mechanism by which HPC selectively gels OA. The results showed that hydrogen bonding occurs between HPC and OA. Analysis of membranes using a scanning electron microscope. It showed that membranes formed by HPC and OA had a unique sponge-like structure. Kao also speculates that the gelling may also have occurred because a significant amount of OA was taken into the spaces of the sponge-like structure formed by the bonding of HPC and OA. It is expected that trapping OA on the skin surface may reduce its contact with the skin, thereby reducing its negative effect on the skin.
Kao clarified in this research that the quantity and quality of sebum can affect the skin barrier function and water content. It was found that skin with a certain quantity of sebum and a higher ratio of unsaturated fatty acids has lower skin barrier function and water content. In the process of research, it was also discovered that HPC could be used as an effective means to trap unsaturated fatty acid, a component of sebum that negatively affects the skin. Kao will apply these findings to the development of new skincare products. They will also focus on solving rough skin and skin dryness caused by sebum.
*1 A type of free fatty acid that has 18 carbon chains and one double bond (C18:1) such as 8Z-octadecenoic acid and oleic acid
*2 Surveyed by Kao between May and June 2021, targeting 129 Japanese females with different skin types between the ages of 20 and 55
*3 65 subjects with 5μg/cm2 or greater sebum secretion 90 minutes after face washing, and 60 subjects with less than 5μg/cm2 sebum secretion 90 minutes after face washing
Source: Kao
