foot pads for detox

I was given a free sample of the foot pads and they turned dark brown. I also was thinking it probably does this for everyone, everytime they do it. However, I did read where someone did it for 10 days straight with them turning brown. After 10 days, the pads remained white even after staying on overnight. Has anyone heard this? I left mine on overnight with a sock on my foot to hold it in place better.

Caroline