PEG-100 stearate is an ingredient in some cosmetics and personal care products including facial moisturizers, sunscreens, anti-aging products, sunless tanning products, body cleansers, shampoos and conditioners. It is made by modifying a fatty acid called stearic acid. In these products, it acts as an emulsifier and an emollient. It falls into a class of compounds called polyethylene glycols, compounds that function as surfactants in products. PEG-100 stearate is a polyethylene glycol ester.
PEG-100 stearate functions primarily as an emulsifier and emollient. Most cosmetics and personal care products contain both water-soluble and oil-soluble ingredients. Without emulsifiers like PEG-100 stearate, these ingredients would separate from one another, creating a product that does not function properly. PEG-100 stearate allows these incompatible ingredients to co-exist stably in a product without separation. PEG-100 stearate also has emollient properties. Emollients function as moisturizers, helping to fill in the spaces between skin cells to create a smoother surface.
There are some concerns about the safety of polyethylene glycol esters including PEG-100 stearate. The Environmental Working Group classifies it as a potentially hazardous ingredient, although the Cosmetic Ingredient Review Expert panel, an independent group of experts that evaluate the safety of cosmetic ingredients, deems it to be safe in the amounts added to cosmetic and personal care products.
Polyethylene glycols, including PEG-100 stearate, have been found to contain potentially harmful impurities including heavy metals, ethylene oxide and dioxanes. These are compounds linked with a higher incidence of cancer and other health issues. Products that contain PEG-100 stearate may be harmful if they are applied to an area of broken skin like a cut, burn or abrasion and should only be used on healthy, intact skin.