"Skin like buttermilk" isn't a line from a corny Elizabethan poem; it's a compliment you might actually get by bathing your skin in the stuff.
That's because buttermilk contains lactic acid, one of the hyrdoxy acids. If you've spent any time looking for a skin-improving lotion, you've no doubt come across alpha-hydroxy and beta-hyrdoxy acids on the ingredients lists. These compounds act as exfoliants on the skin, breaking apart and removing dry, dead skin cells so fresher, younger, moister ones can come to the fore.
But you needn't soak in a bath of sour milk like Cleopatra used to do to see the benefits. All you need to do is wet a face cloth in cold buttermilk (regular milk will do also) and lay it on a dry or irritated patch of skin for about five minutes. Rinse gently, so some of lactic acid stays behind, and voila -- relief from your refrigerator!