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Why Do Onions Make You Cry?

Onions sit on a cutting board.
NUM LPPHOTO/Shutterstock.com

Whether they’re going in a soup or stew or are included in a casserole, onions are one of the hardest foods to prep. Not because they’re difficult to chop, though, but because of all that crying! But what actually causes it?

If you’ve ever wondered why onions make you cry, it’s all about the gases they emit when cut—and it’s actually pretty cool.

Onions are grown underground and to be safe from bugs that might want to take a bite, the vegetable has enzymes and sulfenic acid that come out when the skin is broken. When they combine, a gas called propanethial S-oxide is produced, and it’s irritating to the sense.

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Of course, you can also opt for a quick chopper to avoid tears.

When that gas reaches your eyes and the watery top layer in them, it becomes sulfuric acid. To protect yourself from the acid, your eyes water to flush it out. That’s why you cry.

But if chopping onions is your most dreaded food prep task, there might be ways to mitigate the crying. One option is to place a wet paper towel by your chopping station. Supposedly the gas will be drawn to the water in the towel and less to your eyes. The second option is to switch up your chopping method and try cutting your onions root to stem (instead of orbitally or through the center) to prevent rupturing more onion cells.

Next time you’ve got a soup or casserole that calls for onion, you might want to test out one of those crying prevention methods. You might just take onions off your no-go list of foods.

Shea Simmons Shea Simmons
Shea Simmons is the Assignments Editor at LifeSavvy. Previously, she worked as a freelance writer with a focus on beauty and lifestyle content. Her work has appeared in Bustle, Allure, and Hello Giggles. Read Full Bio »
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