When there are so many options, how do we know what will work for our skin type ? Should someone with sensitive skin be using it as much or in as high a concentration as someone with dry skin? And does age come 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 divine infinity. 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."