Glycolic Acid
It is one of the smallest and simplest AHAs and can penetrate well through the layers of the skin. It is an effective exfoliant and increases collagen synthesis.
Journal Der Deutschen Dermatologischen Gesellschaft, , Volume 10 (7) – Jul 1, 2012, Cosmetic and dermatologic use of alpha hydroxy acids
The Journal of Dermatology, , Volume 25 (2) – Feb 1, 1998, The Effect of Glycolic Acid on Cultured Human Skin Fibroblasts: Cell Proliferative Effect and Increased Collagen Synthesis