Just read that on facebook: (I am translating the text, as it was shared in Portuguese)
The danger you never knew from onions
There is a thing we do and it is so dangerous! ONIONS!
In 1919, when the flu killed 40 million people there was a doctor that visited may farmers to see if he could help them fight the disease, because many of them had already died from it.
Visiting another farmer’s property in the same region the doctor was surprised to see the healthy family living there. Everybody was really healthy. When the doctor asked the farmer what they were doing to protect themselves from the flu his wife told him that she was putting a chopped onion (with the skin on) in plates in each room of the house. The doctor could not believe what he heard. He asked the farmer for one of those onions and put it under the microscope, when he saw a large number of flu bacteria accumulated on the onions.
He took them to a colleague, who explained that onions are like a huge magnet for bacteria, especially when raw.
Therefore, do never keep sliced onions to be used on the next day, even when put in closed bags, Tupperwares or in the fridge. You have to use them right away. Besides that, dogs should never eat onions. Their stomachs can’t metabolize onions.
Remember: It is dangerous to bla bla bla (text keeps going on about flu bacteria and magnets and that they can give you the hibbie jibbies and make you shit water).
This is so stupidly wrong that I had to share with you guys.
I see flu bacteria through the microscope all the time.
Fortunately I have lots of cupcakes lying around to keep them from getting out of hand.
One of the most pervasive influenza myths is spread by homeopaths who claim that homeopathy was highly successfully treating the Great Influenza of 1919 (evidence for this is, to put it politely, lacking). Not too surprisingly, I found a homeopathy website that refuses to dismiss the onion myth either.*
*note that this site references Snopes regarding the belief that onions prevent flu, but somehow fails to mention that Snopes dismisses the claim as false.
That makes it sound like onions just cause an upset stomach. Onions and garlic and other things in that family are not good for dogs or cats because they cause a Heinz body anemia. The Heinz bodies cause destruction of the red blood cells. Cats are more sensitive but a little bit of onion or garlic won’t be an issue for a dog, like if it steals your Philly cheesesteak off your plate. Dogs would have to eat a lot or have chronic exposure for it to be an issue.
See, you’re not thinking about how homeopathy “works.” The more diluted the better. Thus, sparse evidence is millions of times more powerful than strong evidence.
I’ve seen this one too. And a Facebook friend recently posted a variation - before you go to bed, place a slice of onion on the bottom of your foot, then put on a sock to keep the onion in place. In the morning all your ills will be cured! You’ll feel great! And then continued with the nonsense about cut onions being cootie magnets, blah blah blah.
There was no advice about how to keep your bedroom from smelling like onions.
Conscientious use of onions has driven the dreaded influenza bacteria to extinction. We are now left with the only the influenza virus.
If people would only use more pomegranates, we could see the influenza virus eradicated in our lifetime. Then there would still be the influenza prions.