What it is
Sodium acetylated hyaluronate is a derivative of hyaluronic acid in which some of the molecule's water-loving hydroxyl (-OH) groups are replaced with acetyl groups, giving it a mix of water-loving and oil-loving (amphipathic) character. This change lets the molecule behave as a humectant while gaining better affinity for the skin surface, where the acetyl groups act as tiny anchors that help it cling rather than rinse away. Formulators favor it because it is described as less sticky and more cosmetically elegant than ordinary hyaluronic acid. In sunscreens it is used as a hydrating, conditioning ingredient rather than for sun protection.
Safety & warnings
Hyaluronic acid and its salts are widely used as well-tolerated, skin-identical humectants, and the acetylated form is valued in part for a less tacky, more elegant skin feel than standard hyaluronic acid. Published ingredient references for this material do not detail specific irritation or allergen concerns, and as a large water-binding polymer it is generally considered gentle; people with known sensitivities should still patch test any new product.
Origin & sourcing
It is a semi-synthetic ingredient made by chemically acetylating hyaluronic acid, the starting hyaluronic acid for which is typically produced by bacterial fermentation. The acetylation partially substitutes the hydroxyl groups of the hyaluronate with acetyl groups, producing a molecule with both hydrophilic and lipophilic regions.
Questions everyone asks
How is it different from regular hyaluronic acid?
Some of hyaluronic acid's water-loving groups are swapped for acetyl groups, which makes the molecule cling better to the skin surface and feel less sticky than ordinary hyaluronic acid.
Does it provide any sun protection?
No. It is not a UV filter. It is included in sunscreens as a hydrating, conditioning ingredient, while dedicated UV filters do the sun protection.
Is it suitable for sensitive skin?
It is a hyaluronic-acid-type humectant generally regarded as gentle. As with any ingredient, patch testing a new product first is sensible if your skin is reactive.