Moles on fingers are usually caused by abnormal secretion of melanocytes, excessive exposure to ultraviolet rays, and localized foreign objects. 1. Abnormal secretion of melanocytes: abnormal secretion of melanocytes in the hand leads to excessive deposition of melanin, resulting in finger moles, which are usually black in color. 2. Excessive exposure to ultraviolet rays: prolonged exposure to ultraviolet rays in the outdoor fingers, if you do not do a good job of sunscreen measures, may lead to local skin melanocyte degeneration, finger nevus situation. 3. Localized foreign body: finger muscle layer has a blood clot or foreign body, may also appear finger moles. Moles on fingers are benign hyperplasia of pigment cells, which usually do not develop rapidly and do not have any effect on the body. If the mole on the finger has other discomforts, you should consult a doctor for a clear diagnosis.