Q: Can raw onion prevent the flu?
A: A wives’ tale that dates back as far as the 1500s claims that placing a cut raw onion in rooms 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.”
While false, this belief about Onions & Flu remained part of folk medicine through the 19th century, claiming to ward off epidemics such as smallpox, influenza, and other “infectious fevers.” As well an anecdote from the 1919 influenza epidemic claims cut onions placed around the house will fight off the flu virus. Cold and flu viruses are spread by contact, not by floating in the air where the onion can supposedly attract or destroy them.
In fact, when cut, onions release compounds that do not promote pathogen growth. The Center for Food Safety at the University of Georgia states that juice released from cut onion is known to kill or inhibit the growth of several types of microorganisms, including some of those capable of causing food poisoning in humans. When handled properly, cut onions can be stored in the refrigerator in a sealed container for up to 7 days.
In short, there is no scientific evidence that a cut raw onion absorbs germs or rids the air of toxins/poisons.