Grilled, raw, caramelized, sauteed, you name it; onions are a staple in almost every household. Their versatile taste and texture make them a key ingredient in countless dishes. But mastering the art of onion prep can save you time and preserve the distinct flavor they bring to your meals. Yet with all this utility comes one common cooking challenge: chopping onions often makes your eyes burn.
Picture this: you’re in the kitchen, effortlessly slicing onions for a fresh salad. The knife glides through the onion’s layers, and in an instant, your eyes sting as tears stream down, blending surprise with the sharp aroma.
Why Does Slicing Onions Make You Cry?
This happens because a chemical compound and an enzyme combine to release a gas when the onion is cut. This is the onion’s defense against predators, protecting the bulb from being eaten.
The culprit in the chemical process is the lachrymatory factor, a chemical that irritates the corneal nerves. When an onion is cut, a compound called cysteine sulfoxides and an enzyme named alliinase are initially separated. However, as soon as you slice, crush, or dice the onions, the barrier that has kept the compound and enzyme apart is broken, triggering a reaction.
The enzyme alliinase turns cysteine sulfoxides into sulfenic acids, which become a gas that irritates your eyes. This quickly triggers pain receptors in the eye and nose, prompting your tear glands to release tears and wash the irritant away.
The eye produces two types of tears: basal tears, which lubricate and keep the eye healthy, and reflexive tears, which flush away irritants. This protects the eye from dust and other particles.
When onion vapor enters your eye, it reacts with the fluid that keeps your eyes moist. The gas combines with lubricating tears, forming sulfuric acid that causes irritation and pain. As a result, your eyes reflexively produce more tears to wash away irritants. Once you understand this reaction, you’re ready for practical solutions that offer relief when it’s time to chop onions.
Another reason onions make you cry: compressing onion tissue releases droplets into the air. As the knife presses the outer skin, it squeezes the soft tissue beneath. When the skin breaks, liquid droplets are released, increasing the chance they reach your eyes.
How Can You Chop Onions Without Crying?
If you’re tired of turning into a crying mess when cutting onions, we’ve got you sorted. Since this is a common kitchen dilemma, there are many ways to chop them without triggering a waterfall of tears. People often suggest tips, such as chewing gum or placing a wet paper towel on your chopping board, but these don’t work for everyone.
Follow The Chef’s Chopping Technique
A 2025 study used high-speed footage of onion chopping. A tear-inducing mist appears at the first cut, followed by slower, more controlled fluids.
Sharpen your knives before you begin cutting. Use a gentle, swift slicing motion, applying only enough pressure as needed for a soft tomato. Avoid pressing down forcefully. Start cutting at the tip of the knife. Remember, the finer you chop the onions, the more juices and vapors are released, so limit cutting as much as possible to reduce tearing.
Use Water
To reduce sulfuric compounds, soak onions in ice water for 30 minutes before cutting. This method lessens tear-inducing vapors, making chopping more bearable. However, soaking can slightly alter the flavor, potentially diluting sharpness and aroma. Cutting under cold water also reduces tears but may be risky when cooking, as wet onions can sizzle unpredictably in hot oil. Weigh tear reduction against potential flavor dilution and cooking challenges to decide if this method suits your needs.
Protect Yourself From Vapors
Switch on a fan or use a cooking hood to ventilate when cutting onions. An old tale suggests holding a piece of white bread in your mouth to absorb onion vapor. While unproven, some people find it worth trying since it seems to help others.
Wear Onion Goggles
If you often work with onions, consider onion goggles. They help prevent tears, but aren’t perfect—vapors can still reach your nose and trigger tearing.
Pick The Right Kind Of Onions
Older onions release more sulfuric acid, so selecting fresh onions can help avoid tears. It is best to choose firm onions with tight, shiny skin. If the skin flakes easily and feels soft, the onion is likely older and more likely to induce tears, and tissues may be needed.
What If None Of These Work?
Well, the unique flavor profile of onions is hard to replicate. Still, if you’re experiencing persistent, uncomfortable, and disruptive eye issues, then you may want to consider alternative options or substitute onions in your cooking. You can opt for precut onions, available fresh or frozen. Grocery stores sell dried onions or onion powder, which work amazingly well. Alternatively, you can try another allium, such as scallions, shallots, leeks, garlic, or chives, that don’t cause crying.
