None. Don’t use them. They are a scam. They don’t remove toxins from the body. They turn “black” because the perspiration in the foot reacts with the pad. That is normal and has nothing to do with toxins.
It is a scam. Its a fraud. A foot detox uses different methods to allegedly remove toxins from the body. It does not work and can not work. There is no research that shows it works and there is no physiological pathway in which foot detoxes actually...