Thanks for writing in.
You seem to have Melasma
It can occur due sensitivity to sunlight.
For melasma as a general rule-
Avoid sun exposure.
Use a good sunscreen of SPF 30 and repeat application every 3 to 4 hours
Take antioxidant and vitamin c
You can apply DEPIWHITE cream at night time over the affected area.
You need to consult a dermatologist
as dermatology being a visual field
, the cause for your pigmentation and the treatment required can only be suggested after proper skin examination.
Few treatments like chemical peeling and dermabrasion
can give you good and long lasting results.