When I Was In Ethiopia, I Used Potassium Carbonate For

when i was in Ethiopia, i used potassium carbonate for the fungus on my neck area which is sometimes lightening and dark in colour. I use this liquid solution and it disappear for the time being and later appear on that the same surface area after six or five months later. I used this liquid solution for about ten years. I don't know the fungus exact name but in Ethiopia It is called 'KOAKUCHA'.what shall i do?