The sudden growth of a mole on the left wrist is considered to be a result of long-term ultraviolet radiation, medication, trauma, and immunosuppression. 1. Long-term ultraviolet radiation: long-term exposure to ultraviolet radiation on the left wrist will stimulate the production of melanin and the symptoms of moles. 2. Drugs: If you use hormonal drugs for a long time, it will lead to the proliferation of nevus cells and cause moles. 3. Trauma: If the left hand and wrist are traumatized, the healing process will lead to benign proliferation of local melanocytes, resulting in moles. 4. Immunosuppression: If the body’s immunosuppression function is impaired, it will lead to a decline in the body’s immunity, which is also prone to melanocyte proliferation and mole growth. Left wrist suddenly grew a mole, there may be other reasons, if there is no discomfort symptoms, generally do not need special treatment, if there is an abnormality, such as rapid enlargement should be timely consultation.