Polyglycerol monostearate is mainly used as an emulsifier and conditioning agent in many cosmetics products.  When a water-based vehicle and oil-based ingredients or vice versa have to be mixed, without an emulsifier those may remain separated. So, when an emulsifier is used it helps the dispersion of oil into water or water into oil in such a manner it looks uniform and remains stable. Polyglycerol monostearate has various -OH groups in structure, plus stearate can be considered a fat-loving molecule. Now, -OH group and some other groups in the molecule of diglycerine tend to hold water molecules along. This phenomenon is particularly helpful in the case of dry skin and hair. When a product containing polyglycerol monostearate is used, it helps to hold moisture and provides that moisture to the skin to get incorporated. This way it conditions the skin/ hair.