Why does slicing an onion make you cry?

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I was just dicing an onion for something I am making for dinner tonight.. and like always, it made me 'cry.' This always happens to me but I've never known why this ...show more
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you cry because Onions produce the chemical irritant known as syn-propanethial-S-oxide. It stimulates the eyes' lachrymal glands so they release tears. Scientists used to blame the enzyme allinase for the instability of substances in a cut onion.

I heard that to prevent you from crying Chop the onion under water, under running water, or pre-soak in water.
This 'under water' lore seems quite pervasive; I cannot imagine trying to hold and contain all the diced onion bits (which float away) under a sink filled with water. In theory if the onion was exposed only to water and not air the sulfoxide would be washed away by the water and never become airborne. A variant is to have running water nearby the chopping area in the hopes that it will obtain some of this aforementioned magical attractive power (this didn't work for me.) Another scheme is to soak the onion peeled (even cut in half or quarters) in water for some length of time to draw out the juices. While this may reduce the fumes some it only penetrates so far; once I started slicing into onion the spray was as bad as before.

Wear contact lenses to shield eye surface from airborne spray.
I don't wear contacts so I can't say firsthand, but they don't cover the whole eye surface (leaving it partially exposed) and don't do anything for the nose. Besides, see the next suggestion.

Don't wear contact lenses.
The acid gets between the lens and the eye for an even more excruciating pain.

Wear swim goggles or a diving mask.
This solution actually works because the particles in the air are prevented from touching your skin. The goggles will only protect your eyes, and with the mask you have to breath out of your mouth. It is cumbersome and uncomfortable, and it doesn't protect any one else in the room.

Use a fan to blow away or suck up the fumes.
If you can get a strong enough fan or cut your onions outside where there is a breeze, I can see this method as somewhat effective. If inside, wherever you blow the fumes (unless it's out a window) will be fumigated. Some say use the fan over the stove top, but it usually isn't strong enough; besides it draws the air up, where your head is likely to be. With a fan it is best to blow horizontally, away from the face.

Place onions in the freezer for 20 minutes before cutting.
When the onion juices are chilled they are less likely to become airborne. This strategy is the most well-known solution to the onion problem, but it simply does not work. Unless the onion is actually frozen, there will still be onion juice sprayed in the air (besides, unless you store them in the refrigerator you have to wait for the onion to chill before you can cut it.)

Put white vinegar on the chopping block to neutralize chemicals.
I tried this method, and it actually works. The stinging in the eyes was almost eliminated, but the smell was not very pleasant. The moist vinegar on the onion interferes with frying, and its flavor may taint some foods.

Burn a candle near the work area.
This rarely-known technique is based on the fact that the candle flame pulls air from around it and sends it up the smoke plume. Although surprisingly effective, a single candle usually cannot handle the large amount of aerosol generated by a lot of dicing or fine slicing. This last technique holds the secret to the final solution.
And now the answer you've all been waiting for:

Place the cutting board next to a gas range and turn on a burner or two.
The heat and flames draw in the onion mist, burn it, and send it up with the rest of the flame exhaust. In the heat the chemical changes such that it no longer irritates the eyes. One could also use the hood exhaust fan while the burners are on. The only drawback with this solution is that some unlucky fools aren't cooking with gas. They could try an electric range on high, but it doesn't really work (better to use several candles instead.) A poor stove arrangement might make it difficult or force you to cut left handed, but it can usually be worked out (and you don't have to stand very close to the flame). As with the fan, you want the flame to pull the onion fumes away from your face. And as pertains to all methods, you want to keep your face as far away from the hacking and hewing action at the cutting board as you can. I have a range with four burners: two on the left and two on the right with a big space between them where I put the cutting board. I turn on the two right burners, stand a bit to the left, and cut with my right hand.

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thanks for the info
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Other Answers (8)

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  • LMAKB Mama!<3 answered 5 years ago
    If cut from the top you don't cry as much.
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  • Mike answered 5 years ago
    As you cut - - it releases a fine mist of aromatic acid Just like pealing an Orange
    cut the top and root and rinse in water
    I believe the internal pressure in the onion has been released and will help you overcome. . the tears
    BUT what do I know
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  • Bill T answered 5 years ago
    Question: Why Do Onions Make You Cry?

    Answer: Unless you've avoided cooking, you've probably cut up an onion and experienced the burning and tearing you get from the vapors. When you cut an onion, you break cells, releasing 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. This gas reacts with the water in your tears to form sulfuric acid. The sulfuric acid burns, stimulating your eyes to release more tears to wash the irritant away.

    Cooking the onion inactivates the enzyme, so while the smell of cooked onions may be strong, it doesn't burn your eyes. Aside from wearing safety googles or running a fan, you can keep from crying by refrigerating your onion before cutting it (slows reactions and changes the chemistry inside the onion) or by cutting the onion under water.

    The sulfur-containing compounds also leave a characteristic odor on your fingers. You may be able to remove or reduce some of the smell by wiping your fingers on a stainless steel odor eater.


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  • Mimi answered 5 years ago
    cuz the acid
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  • Parvathy. (Keerthu) answered 5 years ago
    I don't think so there are tips to prevent this. while cutting onion i used to put my glass (no power) so we wont cry. and why we are crying, that's coz when the water in the onion gets into ur eyes we feel to cry and next question comes whats the specialty of that water that water is too spicy

    regars and wishes............


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  • scoutma53 answered 5 years ago
    Compounds of sulphur in the onion which are released when cut and irritate the eyeball. Some onions are worse than others. I have never found anything to stop the tears - goggles?- all I do is cut them as quickly as possible and try not to blink.
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  • heylo=) answered 5 years ago

    here's a great answer to your question, it talks about the health benefits in onions as well
    also, this sounds dumb, but sometimes i wear sunglasses or regular glasses while chopping onions and that helps to stop the crying. also, if your just slicing onions for hamburgers, slicing the onion with the peel left on reduces burning and crying as well. just remove the skin before serving. I haven't tried this, but people say chewing gum while cutting onions works too.
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  • MA YA answered 5 years ago
    what i do is i cutter on the faucet with the water running,and i don't cry no more.
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