Onions are plants that absorb sulfur from the soil as they grow. This is a chemical stored within the onion’s cell walls (or membranes). When those membranes are broken by our knives, they release a numerous enzymes and a chemical called amino acid sulfoxide into the air.
These react with the water on the surface of our eyes to create sulfuric acid. Our body is wired to flush out unwanted chemicals or particles from our eyes with tears, so the second our brain senses that pain, it sends the signal to start tearing up.
- How to Cut Onions Without Crying
Always use a sharp knife. The more efficient your chop, the less time you’ll spend exposed to those burning vapors. A sharp knife will do less damage to the onion cells themselves, and slice through them rather than crushing them and releasing more chemicals into the air.
Keep your chopped onion pieces face down and away from your work space. It can really make a big difference.
Try to leave onions in their original position as much as possible when you cut them, so that you don’t increase the surface area of exposed onion flesh. For example, when you first cut your onion in half, make sure both halves are placed cut-side down on the board. And don’t peel that section until you’re ready to cut into it!
- The Best Hacks That Actually Work
The Vent Technique
Why it works: The air circulation directs the onion vapors away from your eyes, so that painful chemical reaction doesn’t happen.
- Freeze ‘Em and (Don’t) Weep
What it is: Stick the onions into the freezer 15 minutes before you’re ready to prepare them, but don’t forget to take them out before they get hard!
Why it works: The cold temperature minimizes the release of chemicals from the onion. The enzymes are less reactive in cold and hot temperatures and that’s why cooked onions never make you cry.
- Drown Your Sorrows
What it is: Peel the onions and let them soak in a bowl of water for 10 minutes.
Why it works: The chemicals are drawn into the water. However, this will also take away some of the characteristic taste of the onions, so be careful when you cook with them.
- The Onion Goggles
What it is: Yes, that’s right! Wear a pair of goggles while cutting onions.
Why it works: Goggles create a sealed barrier between your sensitive eyes and those harsh air-borne chemicals. Some people claim they don’t cry when they chop onions while wearing contact lenses and that also makes sense.