What is it?
An emulsifier made by joining polyglycerin-4, a chain of about four glycerin units, with a mix of isostearic acid, polyhydroxystearic acid and sebacic acid. It helps oil and water blend and stay blended in creams, lotions and other cosmetics, and it can also act as a cleansing agent. Like other polyglyceryl esters, it is built from glycerin rather than ethylene oxide.
Key information
- The CIR has not assessed this exact ingredient, but in its 2016 review of polyglyceryl esters it was not a sensitizer in a guinea pig test.
- The CIR has found its building blocks safe as used, some on condition that products are formulated to be non-irritating: polyglyceryl fatty acid esters, sebacic acid, isostearic acid and polyhydroxystearic acid.
- Polyglycerin is made by linking glycerin molecules, not with ethylene oxide, so this is not an ethoxylated ingredient.
More information
Polyglyceryl esters are made in two steps. First, glycerin is heated with an alkaline catalyst so that glycerin molecules link together and release water, forming polyglycerin. Routes using epichlorohydrin or glycidol exist, but the CIR notes they are less competitive than the glycerin route. Second, the polyglycerin is esterified with acids, here isostearic acid, polyhydroxystearic acid (a polymer of hydroxystearic acid) and sebacic acid. Like PEGs, polyglycerins are polyethers, but they are built from glycerin, not ethylene oxide.
This exact ingredient has not had its own Cosmetic Ingredient Review (CIR) safety assessment. It was not among the 274 polyglyceryl fatty acid esters the CIR Expert Panel reviewed in 2016 and concluded are safe as used when formulated to be non-irritating. That review did use test data on it as read-across for a related ester: it was not a sensitizer in a guinea pig test run to an international (OECD) guideline. The panel noted that polyglyceryl esters are extensively broken down to common nutrients and that some can help other ingredients pass through the skin.
Its components have been reviewed separately. The CIR has found sebacic acid safe as used and isostearic acid safe when formulated to be non-irritating and non-sensitizing. In 2023 it found polyhydroxystearic acid safe as used, relying on its large molecular size, which precludes absorption, and on negative skin irritation and sensitization data. We found no published human patch tests on the finished ingredient itself.
On labels, look for “polyglyceryl-” followed by a number. The “poly” refers to glycerin, as in our polyglyceryl-2 caprate and polyglyceryl-3 stearate entries.
Sources: Cosmetic Ingredient Review: Safety assessment of polyglyceryl fatty acid esters as used in cosmetics (final report, 2016); Cosmetic Ingredient Review: Post-meeting announcement, 164th Expert Panel meeting (March 2023), polyhydroxystearic acid final report; Cosmetic Ingredient Review: Quick reference table of safety conclusions (September 2022)
