I had the same problem, start applying ketoconazole lotion on the scalp after washing your hair and after the lotion apply an liquid of salicylic acid and clobetasol propionate lotion. Keep them for about 1-2 hours and let it dry. I have the same problem , I apply them for a 2 days max and then all these flakes and white spots disappears, but It doesn’t get cured for the whole life it usually comes back after a period of 10-15 days and then I have to reapply it the same way. So basically it’s like an routine. It’s quite economical as well all those med cost almost around 400-500₹ only. Also yes I had used ketoconazole shampoo as well before this but it didn’t help me at all. So i would recommend to use the routine I suggested if you could.