Vitiligo is whiter after exposure to light, which may be due to the increased melanin secretion of normal skin around the white patches and more severe melanin loss in the white patches, and so on. 1. The melanin secretion of the normal skin around the white spots increases: because the melanin in the non-lesion area is more sensitive to light, resulting in a significant increase in melanin, while the lesion area is less sensitive to light, so the melanin growth is not obvious compared to the lesion area. The two produce a more obvious contrast, resulting in vitiligo after the light more white. 2. white spot melanin loss is more serious: if not assess the white spot lesion situation, the starting value and see the value of the precise assessment of the quantitative, against the efficacy of the light will cause a great negative impact. If blindly light not only can not achieve the effect of treatment of vitiligo, some patients will appear after the light more white phenomenon. Vitiligo after the light more white, there may be other reasons, it is recommended to timely medical treatment, find the reason, according to the reason to adjust the treatment program.