Is this similar to an "ionic" foot bath? Those baths purged out black specks for me on the top of my feet. It also purged the white things out of my feet as well. The lady doing my footbath thought my water was really interesting.. and pointed out the white thing and said.. "that looks like a parasite!?".. all I said was "really?"
Anyway.. if it's the ionic foot bath that you are talking about, then they usually just put a little salt in there for conductivity. I never had an issue with anything spreading... I used it mostly for general detoxing. I still do this once a week.. and there are no more specks or white things out of the feet now!