Staying up late usually leads to an increase in skin melanin deposits. Usually the skin’s microvessels get enough blood supply, the skin’s cell tissues can receive nutrients smoothly, so that the skin becomes glossy. If you stay up late without resting, it is easy to lead to a reduction in the blood circulation function of the skin, unable to remove the metabolites on the skin, which leads to black skin deposits and become rough. In addition, staying up late for a long time can lead to endocrine disorders, which can lead to melanin deposits on the skin. When you stay up late, cortisol, which is responsible for the secretion of oil, is still working constantly, oil is secreted continuously, and oil metabolites accumulate on the skin, leading to melanin deposition. However, the most important cause of melanin deposition and skin darkening is the exposure of the skin to ultraviolet rays. When the skin receives too much ultraviolet radiation from the sun, the ultraviolet rays will stimulate the melanocytes at the base of the skin to become rapidly active, shuttling through the epidermis, constantly coming to absorb the ultraviolet rays to protect the body from damage, so there will be a situation where the skin becomes darker after sunbathing. In daily life, should ensure sufficient sleep time and regular routine, avoid staying up late and sun exposure, in order to maintain good skin condition.