What causes skin blackening?

1. Bad living habits: Because sleep at night is the best time to repair the skin, the ability to absorb nutrients at night is eight times that of the day, so if you don't sleep enough, it will slow down the blood flow of the skin and darken the skin. In addition, eating spicy and pigment foods will also cause skin blackening. 2. UV damage: Due to prolonged exposure to sunlight, melanin is formed on the skin, causing skin blackening. 3. Other factors: Such as pregnancy, irregular menstruation, etc. will also promote the increase of melanin in the epidermis, causing skin blackening. In addition, infection, chronic diseases, liver and kidney diseases will cause skin blackening.