My two 8-month-old kittens have been enjoying our Christmas tree (it's Blue Spruce, which is non-toxic to cats). Now the boy has some spots of sap on his face, and the girl has it on her whiskers! I thought they would lick it off each other, but they haven't after a couple of days. Do I just wait, or is there a magical concoction that can remove it safely? Water alone isn't doing the trick.