Old idea. 40 years ago we used to use silver nitrate on burns: but it did make a mess (turned everything black). Now we use Silvadene instead.
The problem is that you can’t just drink it and expect it to work.
And if you take too much of it, your skin turns grey (not dangerous, but ugly).
Wasn’t it during the Civil War that the first battlefield photographers discovered that silver nitrate used for fixing negative plates also served as an antiseptic to treat wounds?