What Causes A Large Patch Of Discoloration Around The Ear?

Hello, my son (10 yrs old) had a rash around both his ear lobes which the doctors said was due to dust, pollution ..and looked like a red eczema rash with fluid as well.
the doctor asked to use panderm plus cream, which took the rash and irritation away in just about 2-3 applications. but now there is a large area around his one ear that is discolored..can you help me understand what caused that? was it the eczema or the cream and will it get back to normal skin. we are indian origin with my son having olive skin tone