Dullness in skin color is widely regarded as a measure of the beauty of the skin or skin condition. The term "dull skin" is generally used in the cosmetic industry to describe skin that looks dark or yellow, uneven, unhealthy, or lackluster. However, there is no medical definition of dull skin.
The cosmetic industry has a long history of research into the cause of dull skin. Dull complexion can be attributed to various factors, including increased melanin, glycosylation, drying, and accumulated dead cells. These are the findings obtained from studies based on dermatological mechanisms. However, research had not been conducted regarding direct factors that make the skin look dull. At Momotanijuntenkan, we have conducted research on what makes the skin look dull and how dull skin can be improved by eliminating the causes.
The scores of visible skin dullness get worse with age. Our research has confirmed that, as already shown in prior research, dull complexion is correlated with an increase in melanin and an accumulation of dead cells.（Mann-Whitney U-test: p<0.01）It has also been found that the higher the score of visible dullness, the lower KLK5 (protein) is.（Mann-Whitney U-test:0.01<p<0.05）It is considered that a decrease in activity of KLK5 causes delay in the skin cell turnover, allowing dead skin cells to remain on the skin surface. (Figure 1)
The research also shows that when healthy persons used protease solution—which is widely known for being effective in improving skin cell turnover—for 28 days, the activity of their KLK5 significantly increased compared to that of those who did not. (Figure 2) In addition, those using protease solution experienced a decrease in the area of epidermal corneocytes, a barometer for the promotion of turnover, and 87.5% of them felt that their skin dullness had really improved. (Figure 3)
These results suggest KLK5 is closely related to the perceived skin dullness, and they also confirmed a correlation between the turnover of the skin and dullness.
We will use these research findings to develop drug products to improve the turnover of the skin.
|A study of factors involved in the skin dullness
There are various methods to observe the skin, including observation in everyday space, observation with full-face photo equipment under a certain lighting condition, and microscopic observation of skin texture. A combined use of different types of observation methods enables us to obtain an overall picture of what is happening to the skin.
Observations using an ambient light lens show that skin that is slightly swollen and white (skin in the red box in Figure 1) looks "dull in color" to the naked eye. This supports the prevailing theory that a major cause of skin dullness is dead skin cells accumulated due to delay in skin turnover.
|21st JFACE (Japanese Academy of Facial Studies) Annual Conference
|Morphological characteristics observed in dull skin
* An example of research has been provided.