What is the function of zinc oxide in calamine lotion?

"Calamine has a mild astringent action of the skin and is used as a dusting powder, cream, lotion or ointment in a variety of skin conditions. Zinc oxide has a mildly antiseptic action and is a mild astringent, it has soothing and protective properties."

Source; emc (Electronic Medicines Compendium-U.K.)