Why do onions make your eyes tear up?

Answer 1

When you slice through an onion, you break open a number of onion cells. Some of these cells have enzymes inside of them, and when they are sliced open, the enzymes escape. The enzymes then decompose some of the other substances that have escaped from sliced cells. Some of these substances, amino acid sulfoxides, form sulfenic acids, which then quickly rearrange themselves into a volatile gas.

The gas reaches your eyes and reacts with the water that keeps them moist. This changes the chemical's form again, producing, among other things, a mild sulfuric acid, which irritates the eyes. The nerve endings in your eyes are very sensitive and so they pick up on this irritation (this is why our eyes sting when we slice onions). The brain reacts by telling your tear ducts to produce more water, to dilute the irritating acid so the eyes are protected. Your other reaction is probably to rub your eyes, but this will actually make the irritation a lot worse, of course, if you have onion juices all over your hands.

Oddly enough, this volatile compound is also responsible for a lot of the great taste in onions, as well as the pleasant aroma when you cook the vegetable. You'll also get sulfenic acids by cutting up garlic, chives and leeks, among other vegetables, but they don't form the same irritating gas, just a strong smell.

Answer 2

Pretty much it's because the acidic juice...cut an end off an onion and you'll see white juice come out of it at times.... sprays into your eyes while you are cutting the onion irritating your eyes. if you cut both ends off the onion before you chop it this will reduce the spray and you wont tear up as badly if this doesnt work you can hold a whole slice of bread in your mouth so the bread sticks out and it will catch the spray as well.

Answer 3

Well, I remember reading somewhere that an onion's pungency can vary with the sulfur content of the soil. I know that leeks and scallions (also called green onions where I live) are very mild. Spanish and red onions are mild enough that they can be eaten raw. You picked some pretty low-sulfur onions. If you really wanted to be precise I think you can measure sulfoxide content with gas chromotography. I suppose it depends on what level of study we're talking about. Middle school, high school, college? Anyway, if I had to guess from my personal experience, I'd say (from fewest tears to most) scallions, leeks, red onion, Spanish.

Answer 4

The juice of a raw onion produces a gas when exposed to air, which irritates the nose and the eyes. This effect disappears when the onion is cooked.

Answer 5

Don't know but i usually place a glass of water in the area where I'm cutting onion, it stops it from affecting the eyes., strange but true.

Answer 6

Because the onions contain certain chemicals that are not harmful to humans so that we can eat them.And also since the chemicals or onion juice is very strong.

Answer 7

It's the acids that are emitted in to the air. They're irritants. If you put your onion in the freezer for 10 minutes prior to cutting, it will not do it.

Answer 8

Sulfuric acid in the onions. Yes, it's true!

Answer 9

I think it's just very strong and has a spicy kind of smell and taste that makes you cry and eyes burn.

Answer 10

They don't if you plug your nose.
And a raw potato will taste like an apple if you plug your nose.
Not sure how I know that.....