When there are so many options, how do we know what will work for our skin type? Should someone with sensitive skin be using their acid of choice as much or in as high a concentration as someone with dry skin? And does age play into it at all? "The 'good' acids like hyaluronic acid or citric acids support the skin with moisture, strong anti-oxidative effects, and other valuable benefits," Dr. Sturm says. "The acids that damage the skin, however, cause a serious disruption of its protective barrier and often cause dehydration. They accelerate the cell renewal and cause a long-term effect of the skin thinning out, as the cells cannot divide infinitely. This affects all skin types, but someone with very sensitive skin might suffer a faster negative response, which could lead to serious cases of hyperkeratosis."