Glyceryl Stearate
In plain terms
A waxy emulsifier made from glycerin and stearic acid that keeps oil and water blended into a smooth cream, while also softening skin. It is a gentle, long-used workhorse ingredient.
What the evidence shows
Glyceryl stearate is the ingredient that holds a lotion together: made from glycerin and stearic acid (a fatty acid found in many plant and animal fats), it is an emulsifier that keeps the oil and water phases from separating, and it doubles as a skin-softening emollient. It is one of the most common and best-characterized ingredients in skincare. The US cosmetic-ingredient panel judged it safe for topical use, and human patch testing at up to a fifth concentration found it non-irritating, non-sensitizing, and not phototoxic. It carries no hormone, cancer, or contamination concern, and both the fatty acid and glycerin it is built from are things the body handles routinely. There is little to flag: a gentle, structural ingredient that suits sensitive skin.
On the label
Listed as glyceryl stearate or glyceryl monostearate, usually mid-list as an emulsifier and softener. It is a well-tolerated base ingredient, not an active, so it is rarely the reason a product does or does not suit you.