Alpha hydroxy acids used in many cosmetic products. Glycolic acid and lactic acid are the two most commonly used alpha hydroxy acids. 5 major types of alpha hydroxy acids (and their source): 1) glycolic acid (from cane sugar) 2)lactic acid (from milk) 3) malic acid (from apples or pears) 4)citric acid (from oranges and lemons) and 5)tartaric acid (from grapes)