i have done this!
without the pads, though. it was at a chiropractors office. same idea. you put your feet in a footbath and their is something added to the wwater to pull toxins from your body out from your feet |(gravity, and your feet have the largest pores so you can pull a lot out)
you probably felt not so good after the first couple of times because you may be detoxing too quickly. ether wait a little longer between using them or brave through. its just like die off from any other detox
but i would recommend the bath type. you get to really see what comes out. the heavy metels are black specs that float on top, and the white mucus lookign astuff that floats is waste from the lymph...different colors correlate with different organs...you can really see what needs work