Talk to Dermatologist on Scalp Condition

A white patch has developed on the scalp after hair color allergy. Initially area used to irritate with some sticky fluid like susbtance in the effected area and now has ended up into this patch. It does not irritate/itch anymore and there is no pain. It is now been a month in this condition. Kindly advise suitable oinment, cream or oral medicine to resolve this. Thank you