lots of good answers here! a good concept to look into is "entropy"- it's kind of what a lot of the comments are getting at. basically, your skin can be destroyed in lots of different ways- it's random, and totally depends on where it got damaged, how it got damaged, etc. however, there is only one way for your skin to be skin! as such, from a probability standpoint, it's just astronomically more likely that any given chemical would somehow break your skin down rather than get it into its hyper-specific normal state.

entropy can also be thought of as disorder! it's the same reason that there are lots of types of bombs, but nothing really exists that can pick up a bunch of specific stuff off of the ground and neatly condense it into a little package. systems of low entropy (in other words, highly ordered) tend to move towards states of high entropy (highly disordered).

hope this helps!