Melanin spot refers to the uneven distribution of melanin in the human skin epidermis, and the melanin particles accumulate into clusters or flaky areas, from the external view, the parts with deepened color are called melanin spots. The formation, migration and excretion of melanin particles in human epidermis have their own natural process, and any factors that cause abnormalities in the production, migration or excretion of melanin particles can lead to the formation of melanin spots. The main causes of melanin spots include ultraviolet radiation, endocrine disorders, skin inflammation, late pigmentation, congenital factors and endocrine factors, etc.