What is it?
An ester made by joining glycerin with undecylenic acid, a fatty acid obtained from castor oil. It belongs to the same family of monoglycerides as glyceryl stearate. In leave-on and rinse-off cosmetics it softens and smooths the skin and helps oil and water blend into a stable mixture.
Key information
- The CIR Expert Panel includes it in its review of monoglyceryl monoesters, which it concluded in 2020 are safe in the present practices of use and concentration.
- It is made from glycerin and undecylenic acid, a fatty acid derived from castor oil.
- The EU lists it as an emollient, emulsifier and skin-conditioning agent, with no restrictions.
More information
Undecylenic acid is an 11-carbon fatty acid with a double bond at the end of its chain. It was first isolated in 1877 from the products of distilling castor oil, where it forms when ricinoleic acid breaks down under heat. Reacting it with glycerin gives glyceryl undecylenate, a monoester, or monoglyceride.
The Cosmetic Ingredient Review (CIR) Expert Panel first included glyceryl undecylenate in an assessment of glyceryl monoesters published in 2004. It later re-reviewed the whole family, 44 ingredients made by joining glycerin to carboxylic acids (mostly fatty acids), in a report published in 2020, and concluded that they are safe in cosmetics in the present practices of use and concentration. The panel added one formulating caution: some monoglycerides can help other ingredients pass into the skin, so care is needed when they are combined with ingredients whose safety depends on low skin absorption. It also asked manufacturers to keep pesticide residues and heavy metals low in plant-derived raw materials.
Its parent acid, undecylenic acid, has antifungal properties and appears on the EU’s list of preservatives allowed in cosmetics. Glyceryl undecylenate itself is listed in the EU inventory as an emollient, emulsifier and skin-conditioning agent, not as a preservative, and has no restrictions. On ingredient lists it appears as glyceryl undecylenate.
Sources: Cosmetic Ingredient Review: Safety assessment of monoglyceryl monoesters as used in cosmetics (International Journal of Toxicology, 2020); European Commission CosIng: Glyceryl Undecylenate; European Commission CosIng: Undecylenic Acid; PubChem: Undecylenic acid
