Every home cook knows the moment. You're two cuts into an onion and your eyes are already watering, your nose is running, and dinner prep just got a lot less fun. The good news: onion tears aren't inevitable. Once you know what's causing them, a few small changes to how you prep will fix most of the problem.
Why Onions Make You Cry in the First Place
An onion defends itself. When you cut through its cells, you release sulfur compounds that mix with enzymes and form a gas called syn-propanethial-S-oxide. That gas drifts up to your eyes, reacts with the moisture there, and your tear glands do exactly what they're designed to do — flush the irritant out.
So the whole game is simple: release less gas, and keep what you do release away from your face. These five techniques do both.
5 Practical Ways to Keep the Tears Away
1. Chill the onion first
Pop the onion in the fridge for 30 minutes, or the freezer for 10 to 15, before you cut it. Cold slows down the chemical reaction that creates the gas, so less of it forms in the first place. This is the single easiest fix on the list.
2. Use a sharp knife
A dull blade crushes onion cells instead of slicing them, and crushed cells release far more gas. A sharp knife glides through cleanly and leaves most of the compounds where they belong — inside the onion. If your knife tears the skin instead of cutting it, sharpen it before you start.
3. Leave the root end for last
The root end (the hairy, flat end) holds the highest concentration of the sulfur compounds. Trim the top, peel the onion, and cut it in half through the root — but keep that root end intact while you dice. Cut it off and discard it only when everything else is done.
4. Move the air, or use water
A small fan blowing across your cutting board, or simply working near a running stove vent, pushes the gas away before it reaches your eyes. Cutting near a thin trickle of running water works too — the gas dissolves in water instead of drifting upward.
5. Make clean, confident cuts
The longer cut surfaces sit exposed, the more gas escapes. Work steadily, keep the cut side of the onion facing down on the board between cuts, and don't mill around with the pieces. Fast, clean knife work means less exposure for the onion — and for you.
The 30-Second Prep Most Cooks Skip
Here's the step that ties it together, and almost nobody does it: after peeling, rinse the onion halves under cold running water for about 30 seconds before the first real cut. The rinse washes away the surface sulfur compounds released by peeling and the first slice, and the cold water slows the rest. Combined with a chilled onion and the root end left intact, this quick rinse is the difference between tearing up and barely noticing.
If You Chop Onions Every Day
Technique solves the tears, but it doesn't solve the time. If onions, peppers, and garlic are part of your daily cooking, a press chopper removes most of the knife work entirely: you place the onion on the blade grid, press the lid down, and the pieces drop straight into the container underneath. Less time with cut surfaces exposed means less gas in the air — and dinner prep measured in seconds, not minutes.
The one we carry at Klevaro is the Press Vegetable Chopper — a manual box-style chopper with interchangeable blades and a collection container, so there's nothing to plug in and nothing to assemble beyond snapping in the blade you want. It's $29.99 with free shipping (orders process in 1–3 business days and arrive in 7–15 business days, with 30-day returns by mail if it isn't right for your kitchen). It won't change the chemistry — a very sensitive cook may still want the cold rinse first — but it shortens the job so much that the tears rarely get started.
If daily chopping sounds like your kitchen, you can see it here: Press Vegetable Chopper. And if you're solving more than onion tears, the rest of our problem-solvers are on the Shop All page — every one picked because it fixes one annoying job around the house.