My skin colour was fair but due to ultraviolet rays it becomes black near my face & neck. Suggest tips to fair?

180' wrong! The area which is darker is tanning. The area without as much color has lost it's pigament containing cells. This is called autoimmnune vitiligo. Strongly associated with thyroiditis and pernicious anemia. I get 100 patient questions every summer! only solution, bleach the normally pigmented but darkening (tanned) areas.