So, exactly why do onions make you cry? It’s all about how certain chemicals trigger your vision defense mechanisms. But don’t worry, there are ways you can prevent those watery eyes, and it’s really worth it because onions play such an important part in building the flavor of the recipes included below.

Cutting onions is a kitchen skill every home cook should master.

Everybody has their own defense mechanisms—even onions! When you cut into one, they release chemicals, which react with our own tear glands.

Rough chopped onions are the perfect base for savory dishes.
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Why do onions make your eyes burn?

Chopping onions makes you cry because of the onion’s biochemistry.

Onions contain molecules called amino acid sulfoxides. When onions are growing and maturing underground, they are susceptible to a lot of critters like voles who love to snack on root vegetables. To ward off these threats it releases enzymes called allinases, which change the amino acid sulfoxides into a sulphur compound called sulfenic acid. This happens when the skin is broken and the onion’s cells are disrupted.

By the time the sulfenic acid touches the water layer of your eyes, it has converted into a chemical called syn-propanethial s-oxide (this is also known as a volatile lachrymatory factor).

If you’re like most people, your eyes’ nerve endings don’t like this chemical! They tell the brain they’re experiencing a burning feeling. As a result, your brain triggers its own defense mechanism, using your tear ducts to protect your eyes. Your body is literally doing what it’s supposed to: creating these reflex tears from that burning sensation.

Which onions make you cry?

Technically all onions are tear-jerkers, but some are worse than others. Typically sweet onions are less sulfurous than most. Green onions are probably the most tear-free onions, compared to white onions, red onions, or yellow onions.

So, how can you prevent the waterfalls from flowing?

A knife thinly slices a red onion.

How can I prevent crying from cutting onions?

Don’t fret, onions can’t actually damage your eyes. Check out at these different ways you can prevent fewer tears and tear-stained cheeks!

Freeze Onions

Freezing or refrigerating onions before you chop them slows down the enzymes that kick off that eye-watering chemical reaction.

Eat Bread

If you eat bread while you chop, it’s considered a defense mechanism. How? The sulphuric compounds that are being released from the onion get absorbed by the bread before reaching your eyes.

Onion Barrier

Putting glass or plastic in front of you can prevent the onion’s irritating chemical compounds from reaching your eyes. You can even try those onion goggles if you have them on hand.

Onion Cut

You can always slice away from yourself when chopping onions on your cutting board, so the onion isn’t in your direct line of sight. Avoid cutting the onion’s root end because that part contains the highest concentration of sulfenic acid.

Sharp Knife

Interestingly enough, using a very sharp knife causes less damage to the onion. This makes the onion release a smaller amount of chemical as a result. A dull knife results in jagged cutting that will only leaving you crying longer and harder.

Watered Onions

The most effective way to reduce all those reflex tears is to submerge your onion in a bowl of water 30 minutes before cutting. Keep it at a cold temperature by using ice cubes. You can cut your onion under running water, too.


Working under a cooking hood can be beneficial. Opening a window right next to you while cutting might help as well, especially in cold weather.

Does wearing contact lenses reduce tearing when cutting onions?

It’s definitely a possibility. Think about it this way: contacts cover the cornea, which contains the most nerves and receptors that react to the chemical onions release. So in a way, that could create a barrier.

But on the other hand, contact lenses may disrupt the tear film on your eye, leading to dry eyes. Dry eyes are the onion’s favorite victims because the irritation is that much more painful.

A clear bowl of chopped onions sits on a white cutting board next to a sharp knife.

What are some alternatives to onions?

Depending on how your recipe uses onions, there may not be a perfect alternative. You can always use onion powder, or dehydrated onions that you can stash in your pantry, but the flavor may not be the same. You can also get precut onions at some grocery stores, but the size of the pieces might not be what the recipe calls for.

Bottom Line

Because they’re so integral to the recipes that call for them, it’s pretty hard to avoid cutting onions when you’re cooking. The good news is that onions are not dangerous to your eyes, despite being annoying to prep with. Next time, test out ways you can prevent the crying fits, especially if you have sensitive eyes. And the recipes below are so delicious, they’ll be worth every year.

Frozen sliced green onions are stored in a container.

The Best Onion Recipes

Learn How to Cut an Onion here, and How to Caramelize Onions over there. You can’t miss this Air Fryer Blooming Onion at your next barbeque party (don’t forget to make the Blooming Onion Sauce!). Switch up your hummus with this Caramelized Onion Hummus to go with your Homemade Pita Bread.

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