Why do onions make you cry?

Answer 1

because they are not very nice veg to be around!

fergi

Answer 2

As any chef knows, cooking an onion produces a very strong aroma that most people enjoy. But cutting up an onion stings your eyes and makes you tear up uncontrollably. If you love to include onions in your dishes, you're probably frustrated by this all the time. So just what is it in onions that make them such an ordeal to prepare?
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.

There are all kinds of remedies for dealing with this irritating phenomenon, some more effective than others. As a general rule, move your head as far away from the onion as you can, so the gas will mostly disperse before it reaches your eyes. If you really can't stand the tears, the simplest solution might be to wear goggles. This measure is very effective, but it may seem a bit extreme to those around you, and if your kitchen is steamy, you might not be able to see what you're doing (never a good idea when you're using a knife).

Peeling the onion and then chilling it in the refrigerator before you slice it will minimize the release of gas somewhat, because the change in temperature alters the compounds in the onion. Cooking an onion before you slice it will work also, for the same reason. Another easy solution is to cut the onion under water or run the tap over it as you slice.

Some people say if you hold a lemon, piece of bread or a sugar cube in your mouth, the food will absorb the gas before it reaches your eyes. Breathing with your mouth, instead of your nose, might also help because as you inhale, you suck the gas in and as you exhale, you blow it away. This keeps a lot of the gas from ever reaching your eyes.

Answer 3

It is not the strong odor of the onion that makes us cry, but the gas that the onion releases
The onion itself contains oil, which contains sulfur, an irritant to both our noses and to our eyes. Cutting an onion arouses a gas contained within the onion, propanethiol S-oxide, which then couples with the enzymes in the onion to emit a passive sulfur compound. When this upwardly mobile gas encounters the water produced by the tear ducts in our eyelids, it produces sulfuric acid.

In response to the caustic acid, our eyes automatically blink, and produce tears which irrigate the eye, and which flush out the sulfuric acid.

To prevent the tears, only breath thru your mouth while you cut the onion. I always keep my mouth wide open while cutting. It really helps (it just looks funny, but I don't cry)

Answer 4

When you cut into an onion, you slice through cells which contain
sulfur compounds. Sulfur is quite a noxious (bad smelling)
element. The compounds released are highly volatile, meaning they
quickly enter the air in their vicinity. Your eyes produce tears
because your body wants to wash or dilute the chemicals before they
effect your eyes. The tears are a natural way the body can wash
the offensive chemicals away.
Since there are a variety of onions, we would expect there to be
a variety of amounts and types of sulfur compounds produced by them.
Think of it as different types of apples: some are red, some yellow,
some green, and they all taste a bit different due to different
chemical compositions. Onions are different in that way too.
Some are REALLY bad smelling, some only mildly bad smelling.

One further bit of information. The chemicals which I described above
are both volatile AND water soluble. This means if you cut the onion
while holding it under a spray of water, the chemicals will wash down
the drain and will not enter the air in as great an amount to cause
your eyes irritation.

Answer 5

When you slice through an onion, you also cut through the onion cells. When the cells are cut, enzymes which are normally inside the cell are released. One of these enzymes, alliinase (from Allium the Latin name for onion), then reacts with a sulphur-containing compound known as ‘Prensco', that is also released by cutting the cells. This reaction results in the formation of 1-propenylsulphenic acid, which is further converted by the LF-synthase enzyme to propanethial S-oxide gas. This gas is also known as the Lachrymatory Factor (‘crying factor'), which also explains the name of the enzyme LF-synthase (meaning Lachrymatory Factor synthesising enzyme)

This gas is instable and can react with water which results in, among others, sulphuric acid. When this happens in the eye, the eyes start to neutralise the acid by producing large amounts of water, and thus make us cry.

Answer 6

The crying is caused by oil fumes containing ammonia that irritate eyes and noses. I've once seen a young cook working for Jamie Oliver who used to wear swimming googles when cutting onions because he couldn't stand tears streaming from his eyes, he looked a bit ridiculous. The best way to lessen the irritation is by holding an onion under water when peeling it to prevent the fumes rising to the eyes.

Answer 7

When you cut an onion, the cells break, which releases their contents. Amino acid sulfoxides form sulfenic acids. Enzymes that were kept separate now are free to mix with the sulfenic acids to produce propanethiol S-oxide, a volatile sulfur compound that wafts upward toward your eyes. The gas reacts with the water in your tears to form sulfuric acid. Sulfuric acid burns, stimulating your eyes to release more tears to wash the irritant away.

Answer 8

its the gas thats inside the cells of the onion.
if you put an onion in the freezer for a few minuted before you cut it, it wont be as bad.
also, since i have been wearing contact lenses, i havent cried
cutting onions.

Answer 9

i believe it has something to do with the amino acids in the onion that reacts with the moisture in your eyes. i'm not sure about the name of the acids, but i think thats right if I remember correctly.

Answer 10

because they are so disgusting; the sulfur answers work too