Onion Tears – Make Them Stop!

Onion Tears – Make Them Stop! post image

The tears, the angst… is that onion really worth it?

Lots of great recipes have onions. I know that, I get it. But I don’t like dealing with onions. My eyes tear up, I get sniffly, and my hands smell of onions after.

Why would I go through that?

The flavor, that’s why. Darn it all if those recipes didn’t taste better with those onions in them. Even if the kids picked the onions out, the rest of the meal just tasted better because of the passing acquaintance the onions had with it.  And the same volatile oils that give onions their taste are the ones that cause us our weepy distress.

So I looked up ways to chop onions without tears. I thought maybe there was some trick that the rest of the world used. Judging by the number of posts and Youtube videos (Google “onions and tears” and you’ll get 4.2 million hits), you would think there was some amazing information. Basically it was variants of the same information, over and over. However, I discovered one great way to avoid tears by learning why we cry from onions in the first place.

Why do you cry when you chop onions? When you chop, gas floats up to your eyes, and you cry to flush it out of your eyes.

You know I’m a geek at heart, so here’s the geekery, as I understand it: It all starts with sulfur in the soil. Sulfur is absorbed from the earth into the onion and forms amino acid sulfoxides, sulfur compounds that readily turn into a gas. When you cut into an onion and rupture its cells, the cells release enzymes which convert these amino acid sulfoxides into sulfenic acid. The sulfenic acid then reforms into a chemical (a gas) that triggers your tears.  It also forms odourous compounds, leading to the misconception that it is the smell that triggers the tears.  It is not. The front surface of your eyes has sensory nerve endings to protect your eyes from physical and chemical irritants. When your eyes start stinging or burning, they’re sending a signal to your body that there is an irritant. Your body’s response is sent back to your lachrymal glands, which then release tears to flush the irritant away.

So… you chop, gas floats up to your eyes, and you cry to flush it out of your eyes.

By the way, when you cook onions, the enzymes become inactive – no more gas, no more tears.

So all those tips that people share (and argue passionately about) on how to not weep when you cut onions? The ones that work do one of three things – slow down the rate of the gas forming, suck the gas away from your eyes, or shield your eyes from the gas. Forget all the arguments and the advice that was passed down from generation to generation, here are some tips that all work to a certain extent and why:

1. Freeze the onion first (Why? Cold temperature slows down the rate of the gas forming)

2. Heat the onion first (Why? This will denature, or change, the enzymes)

3. Use a really sharp knife (Why? The cells will be cut instead of crushed, thus less enzymes are released and less gas formed)

4. Cut an onion under running water (Why? The resulting sulfuric substances are washed away)

5. Cut under a fan (Why? The fan sucks the gas away. Note: the same effect would occur if you cut them outside in a breeze)

6. Cut next to a candle (Why? The flame sucks in air, thus will suck in the gases)

7. Try not to cut the root (Why? There are more compounds in the root, although the rest of the onion has plenty to cause a problem)

8. Wear goggles (Why? They shield your eyes from the gas.)

What have I found to be the most effective tip? I’m taking a lesson from Chemistry 101 here: want to protect the eyes from chemical irritants? Wear goggles. Goofy? Yes. Effective? Absolutely. And in fact, you can actually buy onion goggles (I kid you not!). Swimming goggles also work – basically, whatever causes a seal around your eyes will be effective.

Then again, a good cry never hurts!

5 comments… add one

  • Based upon 50+ years of cutting up onions. Place in freezer compartment for ten-fifteen minutes, stand up straight, use a sharp knife and cutting board, cut the top and the root end off and immediately discard, half the onion cutting from top to bottom, peel the halves, slice lengthwise into whatever width you desire, then slice crossways into whatever size you desire. No muss, no fuss, no cut fingers and No Tears. As far as the smell, wet hands in cold tap water, place a teaspoon of table salt in one hand, then vigorously all over both hands for approximately one minute and rinse with cold tap water and dry.

    • Hi Jim,
      I just started a full time job with a frozen foods company that specializes in the area you spoke of. Last night we cut onions for 8 hours and I almost died. We are in a tightly controlled line and the fans are not on high enough to lift the gas…is there any recommendations for a newbie like me to prevent the burn? I was thinking about purchasing some swimming goggles…
      I look forward to your response!
      Frozen in Idaho!

  • Light a candle and have near the cutting board. Try it. The heat from the candle rises quickly creating a updraft. The gasses are attracted to the updraft and will be drawn away from your face, thus no tears. :)

  • Also, running your knife under water prior to cutting and a couple times while cutting your onion(s) keeps you from tearing up. Sunglasses (light coloured or else you’ll cut yourself) help also if worn close to your face.

  • I have issues with this too. My biggest tip, buy the already chopped onions in your grocer’s freezer. They are already chopped, cause no tears, and never go bad. They may not be as cost effective, but I splurge on very few things. ha!!


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