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.

But slicing and dicing these delectable bulbs often results in tears and a runny nose, even if most cooks agree that the end result is worth it.

The tears you shed while chopping onions are not caused by any type of emotion. They’re reflex tears stimulated by exposure to irritants.

Before you cook another stir-fry, read on to learn why onions make you cry and how to avoid the tears that come with preparing this popular kitchen staple.

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.

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.

But just like onions, your eyes are also equipped with a defense mechanism meant to protect them from harm. When the nerves in each eye detect a lachrymatory agent, they generate tears to flush it out.

Some people are more likely to cry when cutting onions than others. If you’re sensitive or allergic to onions or other alliums, your reaction may be more severe or include symptoms such as:

Does the type of onion matter?

There are many different types of onion, including some that produce fewer tears.

The onions that generate the harshest chemical reaction have lots of sulfur-containing compounds. These include yellow, red, and white onions.

Sweeter types, such as green onions, have less sulfur, are less pungent, and produce fewer tears in most people.

Through genetic transformation, crop scientists have also created tear-free onion varieties. While not yet mass-produced, you can find tear-free onions called Sunions in some specialty markets.

As much as they may sting, onions are merely annoying and not dangerous to your eyes.

Even so, you’ll want to treat irritated, burning eyes quickly to eliminate redness and reduce discomfort. Here are some tips to reduce crying from onion irritation:

  • Put distance or a barrier between yourself and the raw onion you’re cutting. Put the sliced onions under glass or elongate your workstation.
  • Rinse your eyes with cool, clean water.
  • Place a cool compress or cool cucumbers over your eyes to help reduce irritation.
  • Use lubricating eye drops to flush out the eyes.
  • Use other sore eye remedies, such as cotton balls soaked with aloe vera gel and water or sterile castor oil eye drops.

First, keep in mind that the length of time you store onions affects their potency and tear-producing abilities. Fresher onions are less likely to cause crying than those that have been stored for an extended period of time.

Here are some other tips for preventing crying from cutting onions:

Cut your onions properly

The way you cut onions may help reduce crying to some extent.

Some chefs recommend slicing away from you so that the onion vapor doesn’t rise directly into your eyes.

However you slice them, 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.

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.

Some people also prefer to cut their onions while submerged in cold water. Just be aware that they’ll spit and sizzle wildly in a frying pan if you throw them into oil while wet.

Other people find that their eyes get less irritated if they run water while they’re cutting onions.

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.

The distinctive taste of fresh onion can be hard to replicate. But you may want to substitute onions in your cooking if they frequently cause uncomfortable, disruptive eye symptoms.

Here are several alternatives and other ingredients you can try:

  • Use precut onions, which are available both fresh and frozen.
  • Use dried onion or onion powder.
  • Opt for another allium that doesn’t cause crying, such as garlic, shallots, scallions, leeks, or chives.
  • Replace the crunch of onion with radishes or celery in salads.
  • Cook with fennel, which provides a velvety, licorice taste, instead of caramelizing onions.

Preparing onions often causes a chemical reaction that results in tears for most people. Some people are more sensitive to onions than others.

Try chilling onions in ice before cutting to help reduce their sting.

White, yellow, or red onions are also more likely to make you cry than green ones. Sweeter onions are gentler on the eyes than those with a more pungent taste.