Shiseido discovers that red light has the effect of promoting proliferation of epidermal cells and reducing inflammation

 Shiseido has discovered that red light has the effect of promoting epidermal cell proliferation and reducing skin inflammation.

Using a 3D epidermal model and a culture model of skin tissue, it was confirmed that red light enhances cell proliferation in the basal layer of the epidermis, suggesting that red light is involved in maintaining epidermal homeostasis. In addition, a human test confirmed that red light is effective in reducing skin inflammation after the stratum corneum barrier is destroyed. Some of the research results were presented at the Japan Society of Aesthetic Dermatology (August 6-7, 2022).

Based on our unique R&D concept of "DYNAMIC HARMONY" and a Human/Earth approach, we are working on the development of "environmental harmony and symbiosis technologies" that aim to create beauty by positively harmonizing and coexisting with the environment. We will clarify the relationship between various environments such as light and the skin, and work to create new value that realizes healthy beauty that is unique to you.

In recent years, the company has conducted a wide range of research on the effects of light such as blue light and infrared light on the skin, including research on photoaging caused by ultraviolet rays. The red light we focused on this time has a longer wavelength than visible light and penetrates deeper into the skin. Since the effect of red light on the outermost layer of the epidermis has not yet been elucidated in detail, we investigated the effect of red light on the epidermis.

First, when a three-dimensional epidermis model was irradiated with red light once to evaluate factors involved in cell proliferation, it was confirmed that the number of Ki-67-positive cells, a protein that exhibits proliferative properties in the epidermal basal layer, increased significantly. Furthermore, when the skin tissue culture model was irradiated with red light multiple times and the same evaluation was performed, it was confirmed that the number of Ki-67-positive cells increased significantly as in the 3D epidermis model. These findings suggest that red light promotes cell proliferation in the basal layer of the epidermis and is involved in the maintenance of epidermal homeostasis.

Regarding the effect of red light, in order to observe events that could not be captured by culture experiments alone, we investigated the effect of red light on the skin after the stratum corneum barrier was destroyed in a human test. We destroyed the stratum corneum barrier of subjects in their 20s and 30s by tape stripping, and then irradiated red light to observe changes in inflammation caused by barrier destruction. As a result, the redness score, which increases due to barrier disruption, decreased in the sites irradiated with red light after 1 hour compared to the non-irradiated sites, confirming that red light reduces inflammation caused by barrier disruption.

In addition, aiming to deliver more red light to the skin, we took on the challenge of developing a base that increases the transmittance of red light while preventing UVA and UVB, which have a large adverse effect on the skin. The newly developed sunscreen base with increased red light transmittance was able to increase the transmittance by about 1.2 times compared to the company's sunscreen base with low red light transmittance.