The best-known polyhydroxy acid — a larger, gentler cousin of the AHAs, derived from glucose.
How it works
PHAs loosen the bonds between dull surface cells the way AHAs do, but their larger molecular size slows skin penetration — research associates gluconolactone with comparable smoothing over time at markedly lower irritation, along with humectant and antioxidant activity the classic acids lack.
Rinse-off versus leave-on
In cleansers it conditions and brightens gently at rinse-off contact times; in leave-on treatments at meaningful levels it functions as a true, if gentle, exfoliant.
Tolerability
The exfoliating acid most often tolerated by sensitive and reactive skin, and less photosensitising than AHAs — sun protection remains sensible with any exfoliation.
Pregnancy and breastfeeding
No established concerns at cosmetic levels; conventionally considered suitable, with the usual advice to keep overall exfoliation modest.
