Suggest Treatment For White Patches On The Face

Hi i am 25 year old, recently i went to mumbai and stay for 20 days from there i getting a very slight white patch in my face and it's about 50 paise coin in size
compare to normal skin it's little bit white in that area.there i have used hotel towels and soaps,right now it is slightly spread.Is there any skin problem or an alergy. Please suggest or give me a medical tip to cure this