Onions Cure Flu

Do Onions Absorb Bacteria That Cause Illness?

Have you heard the theory that placing an onion next to your bed will keep you from getting the flu? Are you curious if onions absorb bacteria? Ever wonder if onions help combat the flu? Do you think an onion will turn black after attracting all of the bacteria? Is it possible that onions have powerful antibacterial, antiseptic properties?

We stumbled upon a Facebook post about onions curing the flu, and wondered many of the same questions. We had to find out if it was true, so we reached out to Ruth MacDonald, PhD, RD, Chair and Professor of the Department of Food Science & Human Nutrition at Iowa State University.

Do onions absorb bacteria and cure illness?

Dr. MacDonald: “No, onions do not absorb bacteria. 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. Onions and garlic are slightly acidic, which could have antibacterial effects if you rubbed the juice on things, but these are much less effective than bleach or chemical antibiotics. Eating these vegetables provides antioxidants that can have health benefits, but they are unlikely to prevent or cure disease.”

The post also mentioned that you don’t need to refrigerate mayonnaise. Is this true?

Dr. MacDonald: “Mayonnaise that is made from eggs needs to be refrigerated. Products made from oils only may not require refrigeration – however, once opened, they will grow bacteria just as any food might, due to exposure from utensils or hands during use. It is best to refrigerate any mayonnaise after it has been opened.

The possible sources of foodborne illness are many, especially in salads, and it is usually not possible to trace it back to the original source; however, modern technology is making that more possible. All foods can carry pathogens, and any food left at room temperature or above for more than 30 minutes can become contaminated to the point of causing illness. Pathogenic bacteria in those foods could grow at that temperature. The increased amount of the pathogen (or a toxin produced by the bacteria) in the food causes the illness when the food is consumed.”

Is it bad to feed onions to dogs, as mentioned in the post?

Dr. MacDonald: “I don’t know if dogs can eat onions – but I do know that stomachs do not ‘metabolize’ onions. The stomach of all mammals provides acid and enzymes that break down food prior to entering the small intestine.”

Previously, we asked Dr. MacDonald if it is OK to use leftover onions. Click here to learn more about the food safety rules concerning leftover onions.

Assorted onions” by Alice Henneman is licensed under CC BY 2.0.

  • Maddie

    This is so NOT true! The onion works, for ppl who are opened minded and know why we would be deterred from this, then you understand! Go get THOSE MEDS at the pharmacy…that’s what the government wants…Early 1900’show don’t lie folks…look at your history in ALL ASPECTS…GOD SPEED!

  • Cora857

    I am experimenting now with onions and I will let you know how it goes. For me, I breathe better just after few hours of onion in front of me, but I am not sick. My daughter on the other hand has cough so I wanted to try and I am leaving the onion in her room overnight. Let’s see what happens. I’ll post results in couple of days.

    • alicia

      did it help?

      • Cora857

        I am sorry, I lost the link. My daughter just started developing cough and after I used the onion in her room the cough never developed. Two days later she was fine. But a week later she had strep throat. So I am not sure if I can say the onions work. However there is a possibility that the bacteria/virus was brought up to the throat from lungs. I am going to have to try this experiment again.

        • alicia

          I also have been boiling onions and hanging them around the house and I put some last month in my daughters socks while she slept and her fever broke by Morning Noone in the house has been sick since I started hanging onions and my 10 yr old was home for a week because his school was closed due to illness but he never did catch anything

  • Tommy Peters

    May as well ask an ayurvedic practitioner if side-effects of antibiotics are imaginary. I suppose debating whether white onions work better than reds or if those yellows, peeled or otherwise, are a better alternative is a question for the alternative medicine man, rather (ahem!) Dr. Ruth MacDonald. It is said the Indian and Chinese ‘empires’ have survived thus far largely due to their (now threatened) food and pharmaceutical ‘security’ but that’s another story.

  • Cindy Gable

    Total thumbs down on this article. Old wives tales endure centuries for a reason.
    I started leaving a cut onion in the counter when my son was 12 and neither of us had as much as a cold throughout until his graduation. Science doesn’t have to “prove” anything to make me believe it works. Besides why would they agree with anything you can do for pennies to stay healthy and deprived the drug manufacturer s of all those millios they make poisoning the masses!

  • James Grant

    After reading all these negative comments as well as the article, and eventually will be going into medicine myself… I have come to wonder that maybe the article as well as the comments are both true. Perhaps it’s not that the onion is absorbing the bacteria from our bodies, but rather the onion is releasing beneficial molecules into the air which we then breathe in and helping us to fight off the bacteria. I could be wrong, but to me that is what makes the most sense. Especially if we think about how when we cut an onion for dinner or whatever other purpose, we tend to tear up. It’s not because we feel bad for the onion (lol) but rather wouldn’t it be because we are breathing in what the onion is releasing? Just a thought. 🙂