evidence: Do we need to put onion on our feet overnight? No, that's not true: A number of websites and videos claim placing a sliced onion in your sock while you sleep delivers miraculous health benefits, including detoxifying your blood and making your feet smell better, but there is no evidence the process does that. [...] This is why you should put a slice of onion on the sole of your foot before you go to bed:This unusual method will literally heal you in your sleep.Take a red or white onion and cut it into flat slices.You want to make sure the onion slices can easily be applied to the bottom of your feet.Place the onion slice on the bottom of your feet and put on a pair of socks to keep them in place.That's it! As you sleep, the healing properties of the onion will sleep into your skin and absorb unwanted toxins that can make you sick.It will also work to purify the air in your bedroom and eliminate bacteria. [...] A: There is no scientific evidence that a cut raw onion absorbs germs or rids the air of toxins/poisons. A wives tale that dates back as far as the 1500s claims that placing a cut raw onion in rooms throughout a residence could protect its occupants from getting the bubonic plague. Long before germs were discovered, the dominant belief was contagious diseases were spread by miasma, or "noxious air."