 Zinc oxide paste is superior to gelatins used in other dressings, because it does not harden or cake.Some Unna Boots also contain calamine lotion and glycerin.For venous stasis ulcers, the paste-impregnated wrap is covered by an elastic layer, generally an elastic wrap ("ACE" bandage) or self-adherent elastic bandage such as Coban; this is referred to as a 2-layer compression bandage.