What it is
Gluconolactone is a type of Polyhydroxy Acid (PHA).
What it does
Gluconolactone is an exfoliant. It gives similar results to Glycolic Acid, but without the irritation, making it more suitable for people with sensitive skin.
In addition, because Gluconolactone is composed of several water-attracting hydroxyl groups, it is also able to hydrate skin.
One study has also found Gluconolactone to be as effective as Benzoyl Peroxide (but less irritating) at treating acne lesions.
Gluconolactone is generally considered to be safe.