I am not sure where I read it, but I remember reading something about an epoxy manufacturer recommending never sanding anything but completely cured epoxy. It seems that sanding epoxy that was not fully cured releases some into the air in the form of dust. This dust since it is not fully cured still looks for something to bond to. It might be your lungs or your skin. They thought that this might be how people become sensitized to epoxy. I don't know if anyone else remembers reading this but I think that it is a good idea to wait to any epoxy is "fully" cured just to be safe.