A humectant is a hygroscopic (the phenomenon of attracting and holding water molecules from the surrounding environment) substance used to keep things moist. Compounds include polyethylene or propylene glycols with or without alkyd ether capping groups on one or both ends, glycerol, sorbitols, etc. It is used to keep products moisturized and affects the preservation of items, which can be used in cosmetic products, food and tobacco (see: Wikipedia).