What it is
Polyglyceryl-4 Diisostearate/Polyhydroxystearate/Sebacate is a diester formed from a mixture of isostearic, polyhydroxystearic, and sebacic acids combined with polyglycerin-4. In cosmetics it acts as an emulsifier and emulsion stabilizer, binding oil and water phases together and reducing interfacial tension so the two stay mixed. It is a PEG-free water-in-oil emulsifier that is used to formulate low-viscosity water-in-oil lotions, including sun care and pigment-containing color cosmetics, with a light skin feel.
Safety & warnings
As a fatty-acid polyglycerol ester used at the low levels typical of emulsifiers, it is generally considered mild and is favored in part because it is PEG-free, an attribute sought by formulators and consumers who prefer to avoid PEG-based emulsifiers. As with any emulsifier, individual sensitivity can occur, but it is not associated with notable irritation in typical cosmetic use.
Origin & sourcing
It is a synthetic ester built on a polyglycerin (polyglyceryl-4) backbone esterified with fatty acids, namely isostearic, polyhydroxystearic, and sebacic acids. It is supplied as a PEG-free emulsifier.
Questions everyone asks
What does this ingredient do in a sunscreen?
It is a water-in-oil emulsifier that keeps the oil and water parts of the formula blended together, helping give a stable, light-feeling product.
Is it PEG-free?
Yes, it is described as a PEG-free emulsifier, which is why it appears in formulas marketed as PEG-free.
Is it natural or synthetic?
It is a synthetic ester made by combining polyglycerin with fatty acids such as isostearic and sebacic acid.