COSRX Low pH PHA Barrier Mist is a fine mist that contains 0.5% of PHA (Gluconolactone), which helps your skin maintain its natural slightly acidic pH level and acts as a ‘shield’ to protect and strengthen skin’s barrier. Spray COSRX Low pH PHA Barrier Mist on after your skincare routine, and it will create a mattified, silky barrier to prevent prior skincare from evaporating.