Possible causes of skin melanin deposition include excessive sun exposure, post-inflammatory hyperpigmentation, and internal diseases, which can be removed with the help of medication and medical aesthetic treatments. 1. Excessive sun exposure: When the skin is exposed to excessive ultraviolet radiation, melanocytes in the basal layer of the skin will synthesize more melanin to help resist ultraviolet radiation damage, resulting in obvious skin melanin deposits, such patients should pay attention to strengthening sun protection measures to prevent further darkening, and in severe cases, laser, chemical peeling and other aesthetic treatments to help remove melanin deposits. 2. Post-inflammatory hyperpigmentation: Facial acne, rosacea, folliculitis and other inflammatory skin diseases such as poor healing will lead to post-inflammatory hyperpigmentation, which will show symptoms of localized skin melanosis. Such patients can apply topical hydroquinone cream, azelaic acid cream, vitamin A cream, arbutin and other creams to help lighten the melanin pigmentation, and in severe cases, laser treatment to help improve. 3. Internal diseases: many kinds of liver and kidney diseases, adrenal-related diseases and other internal diseases will interfere with the patient’s melanin metabolism, thus leading to the phenomenon of localized melanin precipitation, such patients can be hepatoprotective drugs (reduced glutathione), glucocorticosteroids (Prednisone), etc., to carry out primary treatment, which can help to effectively improve the localized melanin precipitation of the skin. It should be noted that the above treatment and medication should be carried out under the guidance of a physician, do not self-medication.