People,
I think that we have brought up these pages before, but there never was much jawbone about the specific subject matter.
I feel that folklore is a good source of information.
https://sites.pitt.edu/~dash/scanchange.html
The Sweedish legend begins thusly: "Every intelligent grandmother knows that the fire must not be allowed to go out in a room where there is a child not yet christened; that the water in which the newborn child is washed should not be thrown out; also, that a needle, or some other article of steel must be attached to its bandages [diapers]. If attention is not paid to these precautions it may happen that the child will be exchanged by the trolls, as once occurred in Bettna many years ago."
I have heard quite a bit about steel and iron being a repellent of underwold creatures, and what if our "vibrations" or something like that is captured by water; perhaps to be found in sweat or body oils. Hydrogen atoms are a safe haven for electrons, and attractive to electrons, too. Who knows? Perhaps changelings can be produced with molecular information taken from bath water.
We should not automaticallyreject folklore just because it sounds too outlandish.
Cheers!