Ginger will undergo a series of chemical changes in the process of decay. Among them, there is a toxic substance called safrole, which is a highly toxic organic substance that can denature liver cells.

Since oral administration is toxic, external use is equally toxic. Because it is rotten ginger, it will not change even if it is used externally.

Moreover, the effective components of rotten ginger are gone, and even if it is used harmlessly, it has no effect.