When it comes to AHAs, lactic acid has one of the larger molecules in the group, which means it can’t penetrate as deeply as others. This means all of the hard work of the acid happens on the surface of the skin, which decreases the amount of irritation and helps to protect the skin barrier. So, no matter whether you have sensitive skin or not, if you’ve found that other AHAs cause irritation, try swapping for the gentler lactic acid with the same benefits. “Lactic acid is formed by a fermentation process of using bacteria to convert sugars like glucose in lactic acid,” Marmur says. “It can be a white powder or a clear liquid and can be formulated with compatible ingredients in serums, creams, cleansers, and chemical peels.” And although it is naturally found in dairy products including milk and yogurt, most of the lactic acid we find in topical skin care products is synthetically produced. Another issue: AHAs make your skin more sun-sensitive. “There are certain things you use in your routine that make your skin more photosensitive, meaning your skin burns easier, and those include AHAs,” says board-certified dermatologist Whitney Bowe, M.D. Marmur also warns that some people find lactic acid makes their skin more sensitive to the sun2, so applying SPF is super important. “Make sure to be extra careful with the sun and use mineral SPF 30 or higher.”
