Illustration of glycolic acid molecules. Glycolic acid is a type of alpha hydroxy acid (AHA) which occurs naturally in certain foods. It can be used to treat various skin conditions, primarily acne. It works be separating the outermost skin layer, including dead skin, from the rest of the cell layers of the skin. It is, however, Photographyt always effective and can cause swelling and irritation. Atoms are represented by spheres and are colour coded: carbon (grey), hydrogen (white) and oxygen (pink).