Magnetic therapy is completely based on theory and is still in a pseudo-scientific category. There is no scientific evidence to prove they cure aches and pains. They act as a placebo for people who truly believe they work and that is fine, people can believe what they want but if you want the truth it’s up to you. The story goes that because we have iron in our blood, having a magnetic force surrounding an ache or pain helps the flow of blood within the muscle. But to answer your initial question I’d say take them off before washing so the metal doesn’t become discolored from rust that might rub off onto your skin. I hope they work for you!