The best ways to cut onions without crying

  • When you cut an onion, it releases irritating chemicals into the air that make your eyes water.
  • There are tons of theories about preventing bunion tears, but only a few are effective.
  • Experts recommend using a sharp knife for cutting, refrigerating your onions, or investing in special gadgets.

It’s happened to the best of us: you’re in the kitchen, chopping onions for your dinner, when suddenly tears are flowing and your eyes are burning.

“All foods have a defense mechanism,” says Brian Chau, a independent food scientist and food systems analyst with a master’s degree in food systems and society from Oregon Health & Science University.

Onions have evolved over time to be watery, but preparing such a delicious – not to mention common – ingredient doesn’t have to be a bloody story. Once you understand why onions make you cry, prevention is relatively simple.

“Some people are more sensitive to [onions] than others, which can cause them to produce more tears,” says chef Julie Andrews, MS, RDN, CD, FAND and creator of The healthy epicurean.

Why do onions make you cry?

Close up of different types of onions in a basket.

Different types of onions release different amounts of gases that cause tears.

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The tearing properties of onions are more than an annoyance. “Onions have evolved a biochemical pathway to protect themselves from predators,” Chau says. When you cut the cells from an onion, they release the enzyme alliinase along with a family of compounds known as cysteine ​​sulfoxides, Chau says.

Through a series of subsequent chemical reactions, a volatile gas called S-propanethial oxide is created and spreads through the air.

“The body’s reaction to gas touching the surface of the eye is to create tears to flush the gas out of the eye,” Andrews explains. However, not all onions are equally irritating: sweet onions and green onions contain less sulfur than red, white and yellow onions, so they tend to cause a weaker reaction.

4 proven tips for not crying

Person about to cut off the end of a yellow onion on a cutting board.

One of the best ways to avoid onion tears is to use a sharp knife.

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Scientific solutions exist, but a quick online search for onion remedies may lead you to “tips” based more on optimism than biology. In order to ward off or reduce tears, you will first need to prevent the irritating gas from being released or from reaching your eyes.

These expert-approved tips are ranked from easiest to hardest, but note that because everyone has a slightly different reaction to onions, some techniques may be more effective than others.

1. Use a sharp knife

Keeping your knives sharp is generally good practice, but especially important when working with onions. “A sharp knife does less damage to the flesh of the onion, reducing the amount of gas that is released,” says Andrews.

A dull knife will only make slicing and dicing more difficult, and increase the time you spend around volatile gases, Chau says. Investing in a knife sharpener or buying a new set of blades might not stop the crying completely, but it could keep it from becoming an all-out bloody party.

2. Refrigerate your onions ahead of time

The only thing this trick requires is having enough foresight to put your onions in the fridge before you start cooking. “That may be the best method to try,” says Andrews, and Chau agrees: “Chemical reactions slow down at colder temperatures.”

Place your onion in the fridge for 30-45 minutes and remove it when you’re ready to start slicing. Try to work quickly – as your onions heat up, you might feel your eyes start to sting. Note that keeping onions in the fridge long-term can cause them to spoil faster, so you should only use this method when you plan to use your onions right away.

3. Use goggles

If you’re still having trouble preparing your meals, try creating a barrier between the gas and your eyes. Standard goggles or sunglasses can help, but Chau says eye protection with a seal will be most effective at keeping gas out. Specialized bunion goggles are available and may be worth it just for the laughs, but swimming or safety goggles can also work well.

4. Use alternative cooking utensils

If you can afford it, Chau recommends investing in specialty gadgets. “Buy a good food processor that has an attachment for dicing or slicing,” he says. “You reduce the chances of crying because your exposure time is shorter and sometimes the onions are in a closed environment.” A less expensive alternative is a vegetable chopper, which you can use with almost any type of produce and which will save you a lot of time on preparation.

Demystifying common hacks that don’t actually work

  • Chewing gum. Some people swear by it, but Chau says there’s no scientific reasoning to support this hack because it doesn’t protect your eyes or stop the onion from releasing gas.
  • Soak your onions in water. According to Chau, the water will only hasten a watery reaction, and Andrews notes that throwing soaked onions into a pan could cause hot oil to splatter and burn you.
  • Hold your breath. Breathing in the irritating gas released by your bunions doesn’t cause tears, Chau says — it’s the reaction the gas causes when it hits your eyes. Not to mention the dangers of holding your breath while handling a sharp knife.
  • Microwave your onions before cutting them. Using heat actually worsens the gassy reaction, according to Chau, and could change the taste of your onions.

Insider’s Takeaways

When you cut an onion, it releases chemicals that irritate your eyes and make you cry. There are plenty of bogus tricks out there, but to reduce your risk of tears, use the sharpest knife possible and chill your onion in the fridge ahead of time. If all else fails, using eye protection or investing in specialized kitchen gadgets will save you from becoming a tearful mess.

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