What it is
Lactic Acid/Glycolic Acid Copolymer is a copolyester made by linking lactic acid and glycolic acid monomers into a polymer chain. In skincare and sun care formulas it functions mainly as a film former that helps create a smooth, even layer on the skin, and it can serve as a matrix that gradually releases encapsulated ingredients. As a polymer it is not skin-penetrating in the way its free acid monomers would be, so it does not act as an exfoliating acid in the finished product.
Safety & warnings
As a high-molecular-weight polymer it is generally well tolerated and not associated with the stinging or irritation linked to free alpha hydroxy acids. It is not a known fragrance allergen and is not considered a comedogenic oil.
Origin & sourcing
Synthetic. It is produced by polymerizing lactic acid and glycolic acid, both of which can be derived from petrochemical or fermentation sources.
Questions everyone asks
Does this copolymer exfoliate skin like an AHA?
No. Although it is built from lactic and glycolic acid units, in polymer form it acts as a film former and carrier rather than as a free exfoliating acid.
What is its main role in a sunscreen?
It is used primarily as a film former that helps the formula spread into a smooth, even layer, and it can help carry or gradually release other ingredients.