To prevent crying, it helps to understand why it’s happening. When cutting an onion, a chemical reaction takes place; They damage the cells of the onion, and the leaching enzyme (syn-ropanethial-S-oxide) acts as a lacrimal agent. When this agent hits your eyes, it mixes with your tears to form sulfuric acid and activates your tear ducts to wash out the contamination.
So let it be said:
- Wearing safety goggles is the most obvious answer. It might look a little silly, but it’s the easiest way to prevent the onion’s enzyme from getting in your eyes.
- Sharpening your knife beforehand will limit damage to the onion cells, resulting in fewer gases being released.
- Spraying the cutting board with vinegar will slow down the chemical reaction. It does make your onions smell/taste like vinegar though.
- Always place cut side down to minimize release of chemicals to the outside.
- Slicing onions under the kitchen hood removes some of the chemicals in the air.
- Finally, try not to become emotionally attached to your onion.