What is it?
An emulsifier made by joining capric acid, a 10-carbon fatty acid, to polyglycerin-4, a short chain of about four glycerin units linked together. It helps oil and water mix and stay mixed in both leave-on and rinse-off products. The “-4” counts glycerin units; it has nothing to do with ethylene oxide, so this is not a PEG or ethoxylated ingredient.
Key information
- Polyglyceryl-4 caprate is made from glycerin and capric acid; it is not ethoxylated and is not a PEG.
- The CIR Expert Panel concluded in 2016 that polyglyceryl fatty acid esters, including this one, are safe as used when formulated to be non-irritating.
- In animal tests it did not irritate skin or eyes and did not cause allergic sensitization.
- Polyglycerol esters of fatty acids are approved food emulsifiers (E 475), which EFSA found to be of no safety concern in 2017.
More information
Polyglycerols are generally made by heating glycerin with an alkaline catalyst so that its molecules link together, releasing water. The number in the name reflects the average number of glycerin units. The polyglycerin is then esterified with a fatty acid, here capric acid. The CIR notes that routes using epichlorohydrin or glycidol exist but are not competitive with the glycerin-based process. Like PEGs, polyglycerins are polyethers, but they are built from glycerin, not ethylene oxide.
The Cosmetic Ingredient Review (CIR) Expert Panel reviewed 274 polyglyceryl fatty acid esters in 2016 and concluded they are safe in the present practices of use and concentration when formulated to be non-irritating. It added that proviso because some esters in the group, such as certain isostearates and oleates, irritated rabbit skin. Polyglyceryl-4 caprate itself did not irritate rabbit skin or eyes in guideline tests, did not cause allergic sensitization in guinea pigs, was not mutagenic in the Ames test, and had a lethal oral dose in rats above 2 g per kilogram. It was reported in 19 products at 0.5 to 1.5 percent. The panel noted that these esters are extensively broken down to common nutrients and that some can help other ingredients pass into the skin.
Polyglycerol esters of fatty acids are also food emulsifiers (E 475). In its 2017 re-evaluation, the European Food Safety Authority (EFSA) found that absorption of the intact esters is extremely low, that they are rapidly and almost fully broken down to polyglycerols and fatty acids in the gut, and that they are of no safety concern at reported uses.
On labels, look for “polyglyceryl-” followed by a number, 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); EFSA Journal (2017): Re-evaluation of polyglycerol esters of fatty acids (E 475) as a food additive
