Glyceryl stearate and PEG-100 stearate is a combination of two emulsifying ingredients. The stabilising effect of both means that the product remains blended and will not separate.
Glyceryl stearate is a solid and waxy compound. It is made by reacting glycerine (a soap by-product) with stearic acid (a naturally occurring, vegetable fatty acid). PEG-100 stearate is an off-white, solid ester of polyethylene glycol (a binder and a softener) and stearic acid.
The surfactant qualities of glyceryl stearate and PEG-100 stearate allow oil and water to mix. Creams and lotions are water and oil droplets held together by materials called emulsifiers, without them oil droplets would float on top of the water.
When used in a moisturiser, this forms a protective barrier on the surface of the skin, greatly assisting moisture retention.