SkinCeuticals Glycolic 10 Renew Overnight is a nighttime glycolic acid treatment that delivers a true 10% glycolic acid value to promote cellular turnover for glowing, healthy-looking skin. Glycolic 10 Renew Overnight is formulated with a free acid value of 10% glycolic acid, allowing it to work at a true 10% concentration, which is optimal in promoting effective exfoliation and natural cell turnover.