Short answer: The ionic footbath is unproven, and most likely bunk.
In my wife's role as a Massage Therapist, she's been pitched a number of controversial products and modalities of treatments that reek of quackery. In my opinion, these things detract from the legitimacy of the valuable benefits of things like massage and chiropractic. Yet an increasing number of otherwise professional practitioners are falling for the pseudo-science and monetary allure of these things.
You may have heard of the "ionic foot bath" in one form or another. The basic concept is that you immerse your bare feet in a basin of tepid saline water. Electrodes are then placed in the water with (but not touching) your feet. The process is supposed to "magnetically" and "ionically" draw "toxins" from the pores of your feet. These "toxins" and "heavy metals" then color the water, and you can visibly see these things leaving your body.
The first time that my wife saw this was with several members of her massage class, at the office of a fellow Massage Therapist. This other therapist performed the foot bath on a heavy-smoking friend of hers. The water was stained brown, and smelled of cigarette smoke. They were intrigued.
I was skeptical. I'm always skeptical. I have to see proof. I told my wife that I didn't see any scientific basis for how this could affect any release of toxins. After all, the electrodes are in the water, and not hooked up to the subject. All of the energy and ionization takes place in the water at the electrodes and the water between them. As for the color change, I had witnessed it before as a young amateur chemist, trying to do electroplating. I know that the metals of the electrodes will lose or gain mass, and react with the salt (or other electrolyte) in the water to form colored salts which may or may not be soluble.
Now my wife and I are seeing a chiropractor to correct some back and neck problems. Having never seen a chiropractor prior to this, I'm a bit skeptical of that science, but since my insurance pays for it, I thought I would try it. The chiropractic has helped me tremendously. My wife started after I started to see results. I only found out AFTER she had paid for 10 treatments at a cost of $385 that they had put her on a course of these "ionic foot baths".
Needless to say, not only does the insurance not cover it, but for good reason. It should have been a clue. I was present one day when she finished her foot bath and she showed me the dirty water with little bits of black flakes and white flocculent material. I explained my theory that the water would have changed color most likely whether or not her feet were in the bath at the time. I told her I would show her, so today I did a little experiment:
As you can see in the picture in the upper left, I have a 12 volt battery charger, with two electrodes, one of copper, and the other of steel (a piece of copper pipe, and a nail). In the beaker is room-temperature filtered water with added sea salt (what most peddlers of these products recommend). After only a couple of minutes at most, the water in the beaker appeared as shown in the picture at the upper right: Yellow, with black flakes, and "floaties".
All of this was conducted Without Feet in the water. But I'd seen enough. Another experiment would have been to soak my feet in warm water, and then use some of the water for the experiment. The water would then have contained some of the oil and sweat from my skin, which would have reacted with the Sodium Hydroxide (Lye, or NaOH) produced by the electrolytic reaction to form soap, which in combination with the chlorine and/or Hydrogen bubbles, would have made a nice froth, adding to the nastiness.
I'm not naming the Chiropractor's office that is selling this treatment, because I think they're nice guys who know their chiropractic, but are a little rusty on the chemistry. I'm going to show them some of the other materials I found and see if they'll refund our money and stop trying to sell this quackish treatment.
Want to see some of the products I'm talking about? Use the google search box on the top right of this page to look for "ionic foot bath" and you'll see all sorts of ads and websites for these scam artists. Many of them sell them by MLM as well. For shame.
Want to read about the science of this?
http://www.raygirvan.co.uk/apoth/2004 ... c.html#108575608886281343
Here's a company that ran some experiments to try to prove that ionic foot baths work:
As it turned out, chemical analysis showed no significant difference.
Here's a good article about evidence-based medicine and what it means to have a double-blind clinical study, which is what you would need to prove that a treatment like this worked.