Fresh Red Onions

Why do onions make you cry?

Onions are the third-largest fresh vegetable industry in the United States. Whether chopped, sautéed, or deep-fried, onions find their way into everything from omelets to soup.

Why do onions make you cry?

Onions are bulbs that mature underground. The onions’ subterranean home is inhabited by creatures such as voles, who love to nibble on roots, tubers, and bulbs.

close up of sliced red onion, intended as a background image

To stop this from happening, onions are equipped with a defense mechanism designed to protect them as they grow from hungry animals.

Onions spew enzymes and sulfenic acid when their skin is broken. These compounds combine to produce propanethial S-oxide, an irritating gas.


Propanethial S-oxide is a lachrymatory agent, meaning that it generates tears when it touches the eye. Propanethial S-oxide turns into sulfuric acid when it touches the water layer that covers and protects your eyeballs.

How can I prevent crying from cutting onions?

Cut your onions properly

When slicing an onion, try to avoid cutting your onion near the root end. This is the part that contains the highest concentration of sulfuric compounds that can make you cry.

Female hands cut onions on wooden board

Using a sharp knife may also help. The sharper the knife, the less damage is done to the onion, and fewer irritations are released into the air as a result.

Use water

To reduce or eliminate onion tears, you may have the best luck if you diminish the sulfuric acid compounds in the onion itself. To do this, try chilling your onion in a bowl of ice water for 30 minutes before cutting.

Protect yourself from vapors

Try running a fan to circulate the air or wearing eye protection, such as goggles, while you prepare onions.

Working under a cooking hood, which supplies ventilation, may also help.

One old tale says to keep a piece of white bread in your mouth while cutting, based on the theory that the bread will absorb onion vapor. There’s no evidence for this, but it’s worth a shot.


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