Melanin growth on the face may be caused mainly by a number of reasons, such as long-term sun exposure and increased estrogen levels due to endocrine dysfunction. If you work outdoors for a long time, sun exposure will lead to increased tyrosinase activity in melanocytes in the basal layer of the epidermis. Tyrosinase is a key enzyme for melanin synthesis, which promotes increased melanin synthesis and leads to darkening of the skin. The level of estrogen in the body greatly increases during pregnancy, which also stimulates increased melanin synthesis in melanocytes. When these symptoms appear on the face, you should actively seek medical attention to find the possible causative agent. For increased melanin synthesis, it is recommended to pay attention to sun protection, wear long sleeves, long pants, sun protective clothing, and sunscreen. You can also apply external whitening products such as hydroquinone ointment and arbutin cream.