my son is 7.5.. he has velvety darkness around his neck... dark underarm nd darkness even around his buttocks.is this anythink serious .. plz suggest the reason and remedy if have..?? and ointment if I can apply

A. It is at multiple places I think it could be associated with getting getting dirt accumulated at sometime these places are not cleaned properly so I’m just going to advise you to use a proper soap for home remedy where you can use besan and curd that will help in reducing the darkness and if needed please consult your doctor also