If your have used 10% lactic acid before you can graduate to our 20% lactic acid solution for a peel. Lactic acid is an alpha hydroxy acid that can penetrate skin easily and shed a layer of your skin. You can use it on your entire face every 6 weeks for a peel as needed on trouble spots. Your skin may experience more dryness than normal the days after applying. Make sure to apply sunscreen daily to protect your new skin.