What is it?
A synthetic preservative that helps prevent the growth of microbes in cosmetics and personal care products. It and its more water-soluble salt, sodium dehydroacetate, are used at low levels in eye shadow, blush, face powder, lipstick, skin care and hair care. In the United States it is also approved as a food preservative, but only for cut or peeled squash.
Key information
- Dehydroacetic acid is a synthetic preservative reported at up to 0.7 percent in U.S. cosmetics.
- The CIR Expert Panel found it safe as used in 1985 and reaffirmed that conclusion in 2003 and 2023.
- The EU caps it at 0.6 percent and does not allow it in aerosol sprays.
- In U.S. food it is approved only as a preservative for cut or peeled squash.
More information
Dehydroacetic acid is made synthetically, for example by heating acetoacetic ester. The Cosmetic Ingredient Review (CIR) Expert Panel first assessed it and sodium dehydroacetate in 1985, found both practically nonirritating and nonsensitizing in numerous clinical tests, and concluded they are safe in the present practices of use and concentration. The panel reaffirmed that conclusion in 2003 and again in 2023. By 2023 the acid was reported in 833 formulations and the salt in 1,233, at maximum concentrations of 0.7 and 0.6 percent.
In the European Union both may be used as preservatives at up to 0.6 percent, calculated as the acid, but not in aerosol sprays. CIR’s 2023 re-review document notes that the reason for the spray exclusion is not stated.
The main toxicity questions involve swallowing: the 1985 report described both ingredients as slightly toxic by mouth in rats, and newer studies in rats given the sodium salt by mouth for weeks reported reduced weight gain and effects on blood clotting at higher doses. There are also case reports of skin allergy to creams containing sodium dehydroacetate, one at 3 percent. The panel weighed this newer information in 2023 and reaffirmed its conclusion, noting that allergy reports are few compared with how widely the ingredients are used, and that use concentrations are low.
Reality check: at the low levels used in cosmetics, dehydroacetic acid has a long safety record. On labels, look for dehydroacetic acid or sodium dehydroacetate.
Sources: Cosmetic Ingredient Review: Sodium dehydroacetate and dehydroacetic acid, re-review summary (2023); Cosmetic Ingredient Review: Sodium dehydroacetate and dehydroacetic acid, re-review document with the 1985 final report (2023); U.S. Code of Federal Regulations, 2024 edition: 21 CFR 172.130, Dehydroacetic acid
