Raw onions won’t absorb germs, stop colds, cure flu

Home remedies based around food and drinks, like chicken soup for a cold or ginger ale for an upset stomach, are often passed down from generation to generation. 

VERIFY asked readers about their families’ food folk traditions, and many asked about whether their family’s cold “cures” were backed up by science. 

Multiple VERIFY readers including Michele told us about an alleged treatment for a cold or flu that involves leaving out a raw, cut onion in a room. Another version, which has persisted in blog posts and YouTube videos throughout the past decade, claims you should wear a sock with a raw onion slice in it overnight. The onion slice, according to the theory, is supposed to cleanse your body of illnesses because they claim onions are “known air purifiers.” 

Just how many layers of truth are there to this folk theory?

Can placing raw onions in the house or on your skin cure a cold or flu?

No, placing raw onions in a room or on your skin will not cure a cold or flu.

There are several variations of this old folk belief, and none of them are backed by science. One theory postulates that a raw, cut onion can absorb germs in the air or pull in pathogens. Another claims rubbing onions on a sick person’s feet can pull the germs from that person or “detox” them, and cure their illness. But none of that is true. 

Onions will not pull pathogens out of a sick person or absorb germs out of the air. They also will not trap germs on or inside of your body if you rub them on your feet.

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“Onions do not provide a good environment for bacteria or viruses to multiply or live,” says Verywell Health, a health information website in which all content is reviewed by board-certified physicians. “Even if an onion could draw or remove germs from someone (which is scientifically impossible), there’s nothing special about an onion that would kill these organisms.”

The National Onion Association credits the beginning of this myth to Europe in the 1500s, when many people believed placing raw, cut onions in rooms could protect people inside from getting the bubonic plague. At the time, people believed contagious diseases spread through “noxious air,” because germs weren’t discovered yet.

Some people have expanded on this folk belief by combining it with an ancient Chinese folk medical practice called foot reflexology, said Bwalya Lungu, Ph.D., a food science and food folklore professor at the University of California Davis. Lungu said that people who practiced this ancient medical tradition believed the nerves of the feet were an access point to a person’s internal organs.

So if you were to practice this tradition while believing onions can cleanse the air of germs, then you may think placing an onion on your foot would similarly cleanse your body of illness.

Lungu said that while she couldn’t find any studies that looked into possible benefits of putting onions in a sock, there are two reasons it wouldn’t work: The first reason is that onions don’t actually have these purported air purifying properties, and the second reason is that research shows foot reflexology doesn’t work, and could possibly even make infections worse.

“There’s no evidence showing that indeed the foot is an access point, and the body’s going to absorb compounds and send them to internal organs,” Lungu said. “We really know how the body works, and that’s just not how it works.”

These beliefs are all based around a misunderstanding of how pathogens work. Providence Health & Services, a hospital network, says that the most common ways of getting the flu are through contact with someone who’s sick, or touching a surface contaminated with the flu virus and then putting your hand to your nose or mouth. Those are situations, Providence points out, where raw onions in your room or on your feet wouldn’t help even if they were effective.

Despite this, onions still have some health benefits that can improve how your body fights diseases, just not as air purifiers. But you’d have to do more than put them on your skin.

“They do have their merits for helping you during flu and cold season — as long as you’re eating them,” Providence says. “Onions are good sources of prebiotics. These compounds breed good gut bacteria, which in turn strengthen the body’s immune system to help you fight off any nasty flu bugs. Prebiotics also may help you sleep better and reduce stress — both good outcomes for preventing or recovering from sickness.”