In order to deal with a problem, it is essential to get to its roots! Here is all you need to know about what causes sunspots. 1. Regular exposure to the sun leads to overproduction of melanin in certain areas, resulting in sunspots on the skin. 2. Over-activity of the enzyme tyrosinase, which is responsible for melanin production, also causes sunspots. 3. Sometimes genetics can also be the reason behind the occurrence of sunspots.