From what I learned at school in food preparation, if you cut off the bottom part of the onion (where the root stems from), it releases a strong gas like substance which burns your eyes and/or makes you tear up.
I'm not 100% sure if that is accurate, but it's somewhat relevant.
The chemical that causes the tears is syn-propanethial-S-oxide, a corneal irritant.
Onions Make People Weep - 1907 was released on: USA: October 1907
You cry.Your tears will fall on the onion and it will look like the onion was sweating.
Because the gas evolved from the cutted onions, named syn-propanethial-S-oxide, is irritating for the eyes.
Hello, my name is Sydnee. No, I do not think sticking a bread up your nose makes the tears stop.
No they do not make people sad but they can make people cry - or at least seem to be crying because they irritate the eyes of many people when they cut them up.
The no fears of tears expiriment!
Meatloaf is not actually good for dogs. This is because many people make meatloaf with onions and dogs should not eat onions.
Onions contain sulfur compounds (which also give them their characteristic smell). The compounds are gases and are released when onions are cut. These gases react with the water in the tears in the eyes to form other acidic compounds which irritate the eye and cause crying.
Onions and bellwethers
Adding onions to a food to make the food taste good is a matter of personal preference. Onions help with the digestion of the person eating the food, though.
Approximately 1.1 onions