The skin goes through different phases in 24 hours. During the day, it defends itself against external aggressions like the wind, the sun, the cold, or pollution. At night, it regenerates.
It was evidenced that the highest number of cell divisions occurs between midnight and 1am, and the lowest between 12pm and 1pm. The skin's blood flow is at its maximum between 11pm and 4am, which makes it possible to provide nutrients and remove toxins. And it is between 7pm and 11pm that desquamation on the superficial stratum corneum is the most important.
In addition, the skin has receptors for melatonin which, on top of their role as circadian synchronizers, are excellent at trapping free radicals. In the late 1990s, researchers highlighted the existence of the "Clock" gene as a central regulator for monitoring the circadian clock.
According to Neil Astles, Marketing Manager for biofunctional actives at Ashland Specialty Ingredients, "more than 20% of the expression of a tissue's genes depends on circadian regulation".
"In Asia, it is said that the first three hours of sleep, called 'Golden Time', are the most important for the skin. In Korea, there is also an expression, meaning 'well-slept face', to refer to a beautiful face. It is conveyed by the face of a sleeping woman", explains Florence Bernardin, expert in Asian cosmetics trends and founder of the Information & Inspiration marketing intelligence firm.