I think it is because they have tourmaline in them, the experiences I have had with tourmaline (only in crystal form) was that I was on about 30mg of Mescaline and having a very bad trip. My friend said “hey, Scrump, if you want to snap out of it, this crystal absorbs negative energy rather then transmits it (like quartz or amythesis) The crystal was placed in my hand, and instantly I felt like there was a black hole inside my palm, I could feel the negative energy that was causing my bad trip to flow out of me and into the crystal. After about a minute, the crystal broke in two right in my palm (mind you I was not squeezing it) there were now two crystals. My friend said “Wow, you must have overloaded that thing.” My bad trip went away and now I keep a tourmaline crystal with me at all times. I don’t even have bad days. This is the only reason I can think that they might work. besides the fact that the foot pad turns black after one nights sleep, something is coming out, whether it be heavy metals or something else.