Alpha hydroxy acids (AHAs) are water-soluble acids that can be both synthetically made or naturally occurring. Examples include Glycolic Acid (derived from sugar cane) and Lactic Acid (from milk). They help exfoliate the top layer of your skin, shifting old skin cells to leave you with a brighter, fresher complexion underneath. TIP: AHAs can cause irritation in excess, so start slow - just a few times a week - and work your way up to more regular use if tolerated.