So you may have seen a message going around Facebook that claims you can get rid of diseases and bacteria simply by leaving a cut onion out in the open.  Sadly, like so many things you read on Facebook, this one isn't true.

The message has several forms, but includes stories like a farm family in 1919 who wowed a doctor with their magic onions:

The doctor couldn't believe it and asked if he could have one of the onions and place it under the microscope. She gave him one and when he did this, he did find the flu virus in the onion. It obviously absorbed the bacteria, therefore, keeping the family healthy.

Now, I heard this story from my hairdresser. She said that several years ago, many of her employees were coming down with the flu, and so were many of her customers. The next year she placed several bowls with onions around in her shop. To her surprise, none of her staff got sick. It must work. Try it and see what happens. We did it last year and we never got the flu.

Now, if you like the smell of onions, there's nothing wrong with cracking a few open and spreading them around the house, I suppose.  But it's not going to help you cure diseases. This story has been officially debunked by websites like and, which specialize in proving or disproving these kinds of stories.

The myth that onions can somehow absorb the agents of disease and thereby prevent illness goes back centuries. During the dark and dreadful days of the Black Plague in the 14th century, many believed that a strategically placed onion in a dwelling could indeed ward off the plague. However, this tactic did not "save many from the black plague" as claimed in the message. In truth, onions are no more likely to attract and absorb Bubonic Plague bacteria ... than they are to absorb and attract more modern threats such as the H1N1 virus (swine flu).

Granted, it would be unbelievably cool for such a "magic bullet" to exist to ward off disease.  But unfortunately, the best result you'll get from a house full of cut onions is a pair of watery eyes.