My son was 13 years old and I notice that he always scratch the part of his groin . When I take a look at it , I see white skin then when you continue to rub it white skin falls like a powder . Then after a week it continue to spread down to scrotum . Then a month after I first notice it, it became into a black scar . Then now it comes back again . Any idea what is it and how to cure it :)