Black patches on the skin are mainly caused by excessive skin pigmentation, the specific causes are mainly as follows: 1. Freckles, such patches are small, black or dark brown in color, mostly occurring in children around five years old and more serious in adolescence, the dark patches of skin pigmentation related to genetic factors can be treated by laser. 2. Chloasma, patches are also small and light in blackness, mainly seen in It is mainly seen in pregnant women or women before and after menstruation, and the causes are related to genetic factors, endocrine disorders and ultraviolet radiation.3. Age spots, with larger patches and black or dark brown color, are mainly seen in middle-aged and elderly people, and are a kind of skin degenerative disease, ultraviolet radiation, poor rest and improper diet are the main triggering and aggravating factors.