[noun] Lactic acid is part of the AHA family, an alpha hydroxy acid. It is naturally present in the skin and is frequently used in cosmetics, often as a PH regulator. This means it helps eliminate the bad bacteria found on the epidermal surface so that the remaining bacteria are only those that strengthen the hydrolipidic film. Its keratolytic action eliminates dead cells, making facial skin more even and radiant. This molecule is thicker than glycolic acid and does not penetrate the epidermis as deeply, meaning its action is very well tolerated by sensitive skin.