Onions make you cry when you cut them because they release a gas into the air that irritates the nerves in your eyes.
Many tactics can prevent onion-cutting-induced crying, including using a sharp knife, refrigerating the onion, or soaking the onion in water to minimize the gas produced.
Onion goggles are also a highly effective solution, as long as they're airtight.
Continue reading to get answers to the frequently asked questions about onion tears, including why they happen, what to do about them, and if they're bad for you.
Are onion tears good for your eyes?
When you cut an onion, you break apart all the onion cells and release the onion's juices. This causes sulfur-rich amino acids and enzymes in the onion to interact for the first time, producing unstable sulfenic acids. These acids transform into the chemical syn-propanethial-S-oxide. You can blame that mouthful for your onion tears.
When this chemical vaporizes, it floats into the air and comes into contact with the moisture in your eyes, turning into sulfuric acid (a pungent compound that irritates the nerves around the eyes). As a result, your brain interprets this as a potential attack on the eyes and triggers a tear response to rinse out the chemical.
Don't be embarrassed that a small vegetable made you cry. Onions create syn-propanethial-S-oxide as a defense mechanism to prevent animals from eating them. Your body's simply responding with its own defense mechanism.
Onions may not be doing your eyes any favors when you slice them, but that doesn't mean you should cut them out of your diet. (Did you catch that clever pun?) That's because onions are high in vitamin C, which is essential for your overall immune system and indirectly benefits your eye health.
Can onions damage your eyes?
If you're wondering if cutting onions harms your eyes, the answer is not really. Technically, your eyes do get irritated, and your body reacts with a defense mechanism, so it's not a trip to the spa for your eyes. However, the only real "damage" is that some tears are produced. All in all, there are worse things for your eyes. (Do we even have to mention the number of people who look directly at a solar eclipse? Now, that's harmful.)
How to cut onions without crying
Let's face it. Onions are a critical ingredient in about 99% of recipes so there's no avoiding them when you cook. Luckily, you can try several tricks for cutting an onion without crying.
1. Make the onion cold
Before cutting into it, stick the onion in the fridge or freezer. If you choose the refrigerator, it's best to keep it there for about 24 hours to cool it to its core.
2. Blow the air around
The real issue with onions is that the gas makes contact with your sensitive eyes. One way to address this is to cut your onion next to a small fan or range hood. This helps blow the gasses away from your face so your eyes stay tear-free.
3. Use a sharp knife
A dull knife smashes the onion as you cut it, releasing more eye-irritating chemicals. Using a sharp knife can minimize the gas released. Maybe this is why chefs are so obsessed with sharpening their knives all the time.
4. Put bread in your mouth
This one may sound — and make you look — silly, but it works. Bread is highly absorbent and can soak up the gas from the onion. Just plop a slice of fresh bread in your mouth, with the end sticking slightly out. The bread should be the barrier between the onion's gas and your eyes.
5. Soak the onion
Peel your onion, cut it in half, and soak it in water. When you soak your onion in water for a few hours, it lets the gas mostly dissolve in the water.
6. Wear goggles
Get out those swim or snowboarding goggles. They're not just for sports anymore. Goggles can create a protective barrier and prevent the onion's gas from coming into contact with your eyes. We talk more about onion goggles below.
Do contacts prevent crying from onions?
Unfortunately, anti-onion contacts have not yet been invented. We're sure someone is working on that and planning to showcase it on Shark Tank very soon. Until that happens, you should probably find a solution you can implement today. Luckily, wearing your regular contacts while dicing onions may delay the tears, as there's less surface area exposed for the gas to irritate.
Do onion goggles work?
If you Google whether onion goggles work, you may see some conflicting results. Some say they're the best thing invented for slicing onions since sliced bread. (See what we did there?) And others complain about purchasing a pair and still being left with a damp face.
We believe onion goggles work, but you have to buy the right pair and know how to use them:
Buy a pair that fits close around your eyes without room for air to filter in. For example, some of the better brands have a foam blocker around the edges to block all air.
Wear the goggles tight.
Wearing glasses underneath your onion goggles might push the goggles out and create extra space that allows the gas to get in. Of course, if you're far-sighted, no one should advocate for you to cut onions without your glasses. Consider wearing contacts with your onion goggles to ensure they're effective.
Everyone cooks with onions, but no one enjoys the stinging pain your eyes endure. If you're tired of onions having power over you, you can try some techniques to reduce the gas released. Popular techniques include:
Wearing contacts
Refrigerating the onion
Soaking it in water
Using a sharp knife when cutting
Cutting next to a fan
Or, if you regularly cut onions, investing in onion goggles might be the easiest solution.
If you need to stock up on contacts to ensure you're safe from onion tears, find the same brand of contacts your eye care professional prescribed at 1-800 Contacts.
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Original published date: 4/26/2021
Updated: 11/26/2024
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