All chemical agents can weaken with time on the shelf, and have an expiration date. More important is the results you get from any chemical peel can vary depending on many factors such as pre-op treatment regimen and the number of applications, amount of solution and aggressiveness of the application. All of these components are part of the "art" of chemical peeling. Because of this, you can use a chemical such as Jessner's and get very different results, depending on your goals
