my 5 years old daughter's neck got dark and dry attached is the picture..I am worried about what could be the reason...it is not dirt accumulation

A. Hello good afternoon !! Seems like tan due to sun exposure,apply baby sunscreen lotion . Milk cream and besan or rice flour massage at least once a week . Apply Raw potato juice on the neck or tan area for 15-20 minutes and wash thoroughly to reduce pigmentation.