What it is
Gamma-undecalactone is a cyclic ester (lactone) widely used in perfumery for its sweet, creamy, peach-apricot aroma, and is traditionally and somewhat misleadingly nicknamed peach aldehyde or aldehyde C-14 even though it is a lactone. In cosmetics it serves as a fragrance ingredient, helping build fruity scent accords. It is used at the low levels typical of perfuming components.
Safety & warnings
As a fragrance material it is used at low concentrations in line with fragrance-safety practice. People with fragrance sensitivities may react to scented products generally, so patch testing is reasonable for that group. It is not an oil, so comedogenicity is not a relevant concern.
Origin & sourcing
Synthetic for cosmetic use; the same lactone also occurs naturally in trace amounts in fruits such as peaches.
Questions everyone asks
Why is gamma-undecalactone called peach aldehyde?
It is an old perfumery nickname reflecting its peach-like scent, though chemically it is a lactone rather than an aldehyde.
What does gamma-undecalactone do in a sunscreen?
It acts as a fragrance ingredient, contributing a sweet, fruity peach-apricot note to the product.