How to Cut Onions Without Crying

Prevent watery eyes while dicing onions with these steps.

Chopping onions can be annoying, but it doesn’t have to be.
Chopping onions can be annoying, but it doesn’t have to be. | Capelle.r/GettyImages

When you’re in the middle of cooking your favorite recipe, it’s annoying to have to take a break from chopping onions. But how else can you stand the tear-inducing vegetable? It turns out there are several things you can do to prevent onions from making you cry.

Before learning how to cope with the unpleasant side-effect, it helps to understand why cutting onions triggers tears in the first place. Onions evolved a chemical defense mechanism to turn off predators. When the allium’s skin is pierced, it releases sulfenic acid. The acid reacts with enzymes in the vegetable to create syn-propanethial-S-oxide gas. The gas then reaches your eyes, where it interacts with the moisture that naturally occurs there to produce sulphuric acid and other irritants; we start tearing up to get rid of the substances.

The best solutions prevent the onion’s gases from rising so quickly. Many experts suggest using cold water. Running an onion under the tap while peeling it is one way to avoid tears, but it can get messy. Another option is to pop the vegetable in the fridge for 30 minutes before cutting it. 

Why do cold temperatures work? As Eric Block, author of Garlic and Other Alliums: The Lore and the Science, explained to NPR, “Molecules of any sort tend to move faster when they’re hot and slower when they’re cool—so by chilling the onion, you’re ensuring that the irritating chemicals don't rush up to your face all at once.”

There are other ways to combat the issue. Food & Wine advises adding a little citrus juice or vinegar to change the pH level of the enzymes and make them easier to tolerate. Using a sharper knife ensures fewer cells will rupture, and therefore, fewer enzymes will escape.

You may have been told to wear goggles while cutting onions, but they could be insufficient. Although your eyes are protected, the onion’s burning gasses will still enter your mouth and nose, causing discomfort. 

Read More About Food: