grind 3 parts dried mango powder (amchur) with 1 part rock salt into a thick paste with water; apply daily to the affected patch.
Traditional
On this page Documented — There are human studies behind this ingredient for this particular complaint. Traditional — Carried by tradition and experience; modern evidence for this particular complaint is limited.
All of this is what others have found — tradition, shared experience and the studies done so far. It is not advice given to any one person. Before changing your diet, and especially if you take any medicine, ask your dietician or doctor.
Naturopathy
Keep the area dry and open to air and sun; never share towels.