Sunlight Exposure
Another significant factor that triggers the development of melasma is the prolonged exposure to sun rays. While the melasma symptoms are present during the winter too, but they are more visible during the sunny days of summer. The dark patches resulting due to melasma tend to fade a little during the winter. The ultraviolet rays coming from the sun activate the melanin-producing cells, i.e., melanocytes, to produce more and more melanin and darkens the upper layer of the skin surface.