“…Urea was the most evaluated intervention in the studies, both in isolated use (n = 28) ( 3 , 9 , 12 – 15 , 29 , 30 , 34 , 38 – 40 , 46 – 52 , 56 – 62 ) and combined with lactic acid ( 9 , 14 , 15 , 29 , 30 , 57 , 58 ) , 5% salicylic acid ( 60 ) , and alpha hydroxy acid ( 60 ) . Various concentrations of urea were evaluated in studies, namely: 3% ( 52 ) , 10% ( 3 , 12 , 13 , 29 , 30 , 34 , 39 , 45 – 49 , 52 , 55 ) , 12% ( 12 ) , 12.5% ( 62 ) , 15% ( 56 ) , 20% ( 12 , 30 , 52 , 59 , 61 ) and 40% ( 47 , 49 , 55 , 59 – 61 ) ; however, some studies did not mention the concentration used ( 3 , 9 , 13 , 15 , 40 , 50 , 51 , 56 ) . In some studies, patients were instructed to apply urea cream twice a day ( 34 .…”