Dipentaerythrityl Hexaisononanoate — INCI reference

What it is

Dipentaerythrityl Hexaisononanoate is a fully synthetic hexaester produced by reacting isononanoic acid (3,5,5-trimethylhexanoic acid) with dipentaerythritol, the dimer of pentaerythritol. The compound has CAS number 1051924-91-4. In cosmetic formulations it functions primarily as an emollient, forming a smooth, lubricating film on the skin surface that reduces transepidermal water loss and improves texture. Its highly branched fatty acid chains impart low viscosity and good spreadability, giving products a lightweight, non-sticky after-feel. It also serves as a viscosity modifier, helping formulators adjust the consistency of creams, foundations, and sunscreen bases. The ingredient is used in a wide range of leave-on and rinse-off products including moisturisers, makeup, and UV protection formulas.

Safety & warnings

Generally considered safe at cosmetic use levels. No GHS hazard classifications or precautionary statements are documented for this specific compound. Like other polyol esters, it may cause mild skin irritation or allergic contact dermatitis in sensitive individuals, though such reactions are uncommon. Dipentaerythrityl pentaisononanoate, a structurally analogous compound, was found to be non-irritant in skin tolerance tests but produced slight eye irritation, suggesting products containing related esters should be used with caution near eyes. No evidence of systemic toxicity, mutagenicity, or carcinogenicity has been reported for this ingredient class.

Origin & sourcing

Produced entirely by chemical synthesis. Isononanoic acid (a branched C9 fatty acid, also known as 3,5,5-trimethylhexanoic acid) is esterified with dipentaerythritol (the dimer of pentaerythritol formed by etherification of two pentaerythritol units) under acid or base catalysis at elevated temperature, with water removed to drive the reaction to the hexaester. The starting acid is derived from petrochemical sources via oxo synthesis. No plant or animal materials are used.

History

Dipentaerythrityl polyol esters entered cosmetic use in the late twentieth century as formulators sought stable, high-performance emollients with improved skin feel over traditional lanolin and mineral oil derivatives. The EU CosIng database lists the ingredient and recognises its function as an emollient. A CIR Expert Panel review of isononanoate esters (published 2011) concluded that isononanoic acid esters are safe for use as cosmetic ingredients at concentrations used in practice.

Questions everyone asks

What does Dipentaerythrityl Hexaisononanoate do in a sunscreen or moisturiser?

It acts as an emollient, spreading easily across the skin to create a smooth, moisturised feel without greasiness. It also helps control the viscosity and texture of the finished product.

Is Dipentaerythrityl Hexaisononanoate natural or synthetic?

It is fully synthetic. It is made by chemically reacting isononanoic acid (a branched fatty acid from petrochemical sources) with dipentaerythritol; no plant or animal materials are involved.

Is this ingredient safe for sensitive skin?

It is generally well tolerated. The CIR Expert Panel found isononanoate esters safe for cosmetic use. Sensitive individuals should patch-test any new product, as reactions to ester emollients, though rare, can occur.

What is the difference between Dipentaerythrityl Hexaisononanoate and Dipentaerythrityl Pentaisononanoate?

Both are esters of isononanoic acid and dipentaerythritol, but the hexaester has all six hydroxyl groups of the dipentaerythritol backbone esterified, while the pentaester leaves one hydroxyl group free.