There are many reasons why it will turn dark after being in the sun for a long time.
First of all, ultraviolet rays are the main factor that causes ** to turn black. Ultraviolet rays include UVA, UVB and UVC, of which UVA and UVB are very harmful to **, prolonged exposure to strong sunlight, especially direct summer sunlight, may cause **sunburn, sunburn, and further lead to**darkening. In addition, the darkening is due to the fact that melanocytes accelerate the secretion of melanin when exposed to ultraviolet rays to protect them from ultraviolet rays.
Secondly, the metabolism of melanin is also an important factor that causes ** to turn black. When the number of melanosomes in melanocytes increases, the metabolism of melanosomes will also accelerate, so that more melanin is released to the surface, making it darker. In addition, the distribution and condusation of melanin also affect the color of **.
In addition, the moisturizing capacity and the thickness of the stratum corneum will also affect the tan. If there is a lack of hydration, it can lead to dryness, roughness, dullness. A thick stratum corneum may block the penetration of ultraviolet rays, thereby reducing the production of melanin.
AI Assistant Creation Season In short, the darkening of the sun for a long time is due to the accelerated secretion of melanin by melanocytes caused by ultraviolet radiation, as well as the metabolism and distribution of melanin. In order to protect ** from UV rays, it is recommended to take appropriate sun protection measures in strong sunlight, such as wearing a hat, applying sunscreen, etc.