Abstract
Skin is the outermost organ that is always in contact with the outside world, and is necessarily influenced by external factors such as humidity, temperature, insolation and the trendy factors including suntan and internal factors such as itch and pain. Thus women's skin is likely to be diverse. Therefore, in skincare habits, it is important to know the possible external and internal factors and to respond to them in order to keep healthy and beautiful skin. Hence, to elucidate the difference and changing of skin condition depending on external and internal factors, we investigated 20 years of long-term changes in the skin condition of women in all areas of Japan from Hokkaido Prefecture (43°04'N 141°21'E), the northern part of Japan to Okinawa Prefecture (26°13'N 127°41'E), the southern part of Japan, including total of 5893536 subjects. The results showed that apparent age spots, skin tone and wrinkle condition changed their tendency around 2000. These findings are thought to be attributable to the fashion trends in skin tone (skin tanning (Ganguro) boom to whitening boom) and social awareness of UV-induced skin damage in Japan (In 1998, sunbathing was removed from the recommendation section in the maternal and child health handbook in Japan) . In the case of pore appearance, a possible tendency according to the geographical difference was found. There was the relationship between skin sensitivity and volatility in coenocyte arrangement regularity scores throughout the year. The highly sensitive group exhibited less volatility and the less sensitive group exhibit more volatility.
