Here’s how to prevent onion-induced tears.   

By Corey Williams
Updated: July 11, 2019

We’ve all been there: Even the most stoic among us have been reduced to tears by a seemingly harmless root vegetable. But what exactly is it about chopping onions that makes us weep like babies? As it turns out, you can blame your next onion-induced sobfest on a particularly potent chemical reaction. 

Why Do Onions Make You Cry?

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Onions contain sulfur—that stinky chemical behind a myriad of unpleasant smells, like rotten eggs. They also contain an enzyme called synthase. Cutting into the onion forces the sulfur to react with the synthase, resulting in a chemical compound called syn-Propanethial S-oxide. That compound creates a gas that floats upwards and triggers your tear ducts. 

Though the spontaneous tears can be alarming to those who aren’t expecting them, the eye irritation is nothing to worry about. It should clear up on its own within a matter of minutes. 

Related: The Right Way to Chop Onions, No Matter How You’re Using Them

How to Prevent Crying When Chopping Onions

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While there’s nothing you can do to completely eliminate the eye irritation that comes from chopping onions, there are a few measures you can take to minimize it:

1. Chill your onions before chopping. 

When an onion is cold, the gas it produces is less volatile. Keep in mind, though, that cold or frozen onions are more difficult to cut—so proceed with caution.

2. Cut onions by a window fan. 

Send that gas flow out, not up toward your eyes.  

3. Use a freshly sharpened knife. 

Using a super sharp knife to cut quickly and cleanly will lessen the amount of damage to the onion, which will minimize the amount of gas that escapes. 

4. Wear goggles. 

Hey, whatever works. 

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