What is it?
An oil-soluble form of vitamin C, made by bonding ascorbic acid (the vitamin C molecule) to branched-chain fatty acids. Plain vitamin C dissolves in water; this ester dissolves in oils, so it can be used in creams, oils and other oil-rich skin care. It is often shortened to “THD ascorbate.” In cosmetics it works as an antioxidant and skin-conditioning ingredient, and it is used in skin care products, including eye creams.
Key information
- Tetrahexyldecyl ascorbate is an oil-soluble ester of vitamin C (ascorbic acid).
- Researchers describe it as a precursor that enzymes in the skin may convert to vitamin C.
- The CIR Expert Panel concluded that it and related vitamin C esters are safe in the present practices of use and concentration.
- Allergic reactions appear to be uncommon but have been reported, including from eye creams containing it.
More information
Tetrahexyldecyl ascorbate is made in the laboratory by attaching branched-chain fatty acids to ascorbic acid, which turns the water-loving vitamin into a fat-soluble molecule. It is reported to be more stable than plain vitamin C and better able to pass into the outer layer of the skin. Researchers describe it as a vitamin C “pro-drug”: once in the skin, enzymes inside cells may convert it to ascorbic acid. In other words, it is a delivery form of vitamin C rather than vitamin C itself. For vitamin C in general, see our Vitamin C profile.
It is not immune to breaking down. In a 2021 laboratory study, tetrahexyldecyl ascorbate degraded completely within six minutes when exposed to singlet oxygen, a reactive form of oxygen, unless a second antioxidant was added to protect it. Its measured antioxidant capacity was also much lower than published values for plain ascorbic acid.
The Cosmetic Ingredient Review (CIR) Expert Panel assessed tetrahexyldecyl ascorbate together with six other ethers and esters of ascorbic acid. In its report, published in 2022, the panel concluded that these ingredients are safe in the present practices of use and concentration. Allergic reactions appear to be uncommon, but they happen: a 2022 case report in the journal Contact Dermatitis described allergic contact dermatitis from two eye creams containing tetrahexyldecyl ascorbate. If you have had an allergic reaction to a vitamin C cream or serum, check labels for this name.
Sources: International Journal of Toxicology (2022), via PubMed: Safety assessment of ethers and esters of ascorbic acid as used in cosmetics; International Journal of Molecular Sciences (2021): Tetrahexyldecyl ascorbate (THDC) degrades rapidly under oxidative stress but can be stabilized by acetyl zingerone; Contact Dermatitis (2022), via PubMed: Allergic contact dermatitis to two eye creams containing tetrahexyldecyl ascorbate
