PHA

Polyhydroxy acids, or PHAs, are hydroxy acids with multiple hydroxyl groups. Gluconolactone and lactobionic acid are common examples used for surface exfoliation while also contributing humectant properties.

Their larger, highly water-binding structures are often associated with gentler-feeling exfoliation than stronger AHAs, though concentration and pH still determine tolerability. PHAs are useful for users who want texture support without assuming that 'gentle' means zero irritation.