No, Onions on Feet Won't Cure Sickness

First off, it isn't true that onions "absorb toxins"...

Sliced red onion
Jack Andersen / Getty Images

A viral message making the social media rounds claims that placing sliced raw onions on the bottoms of one's feet and securing them with white socks before going to bed will "take away illness" overnight as the onions absorb toxins from the body. Some also say it prevents the flu.

Description: Folk remedy
Circulating since: January 2014
Status: False

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 claim to the effect that "onions are a magnet for bacteria," therefore, supposedly, "it's not even safe if you put it in a zip-lock bag."

That's just plain false, says Joe Schwarcz of McGill University's Office for Science and Society. "The fact is that onions are not especially prone to bacterial contamination," he writes. "In fact, quite the opposite." According to Schwarcz it's no more dangerous to eat cut onions stored properly in a refrigerator than it is to eat any other raw vegetable stored for an equal length of time.

This is reaffirmed by Dr. Ruth MacDonald, Professor of Food Science and Human Nutrition at Iowa State University. "No, onions do not absorb bacteria," MacDonald says.

"The idea that a vegetable would attract and suck into itself bacteria from the air is not even logical. The onion may turn black because it would eventually rot from both cell breakdown events and bacterial contamination if you left it out, not because it absorbs germs."

And not because it absorbs so-called "toxins," either.

We have not found a single scientific source stating that onions are especially prone to absorbing "toxins" of any kind, much less those specifically related to disease.

A Bit of History

It's true that 500 years ago it was believed that strewing onions around the home protected against the plague, but there are two important caveats to bear in mind: one, that belief was based on an ignorance of what actually causes infectious disease and how it's spread, and two, the theory behind it wasn't that onions absorb germs or "toxins," but rather that onions absorb noxious odors (miasma), which were thought at the time to be the main vehicle of contagion.

The miasma theory began to lose steam as medical science progressed in the latter half of the 19th century, but we still find sources like The People's Physician, a home medical manual published in 1860, stating that raw onions "possess the property of imbibing the morbid effluvia, or noxious exhalations from persons diseased." A few sentences later the author makes this now-familiar recommendation:

Persons threatened with or having seated fevers, should have the half of a raw onion bound upon the sole of each foot at bedtime, being permitted to remain until morning, by which time the slices will have drawn, to a great extent, the febrile disorder from the system.

By the 1880s, references to "morbid effluvia" and "noxious exhalations" were giving way to talk of germs and bacteria, but the onion remedy, albeit slightly modernized, still held sway in some quarters, as in this example from the Western Dental Journal, 1887: "Sliced onions in a sick room absorb all the germs and prevent contagion."

Now, more than 125 years later, we read on Facebook that onions cure disease by absorbing "toxins," as if it's a long-established medical fact.

Regardless whether the agent of infection is thought to be miasma, germs, or toxins, what none of these sources provides is a scientific explanation of how the humble onion could be capable of performing such an incredible absorptive feat. So far as we've been able to discover, there isn't one.

See Also

Sources and Further Reading: