can sliced onions placed on the bottom of the foot help to detoxify the body

Strapping raw onions to your feet probably won’t do you any harm as long as it isn’t used as a substitute for proper medical care, but there’s no scientific reason to suppose it will cure what’s ailing you, either.

The claim that onions are “toxin absorbers” is pseudo-scientific twaddle, as is the related claim that you should never save a leftover onion because “it will absorb all the toxins in the air of your refrigerator.” This is a revised version of an older rumor to the effect that “onions are a huge magnet for bacteria,” therefore, supposedly, “it’s not even safe if you put it in a zip-lock bag.”