Why does cutting onions make you cry?

Answer: Onions release irritating gas

Onions release irritating gas ✓ — Correct! When you cut an onion, you break cells that release enzymes. These convert sulfur compounds into syn-propanethial-S-oxide gas. This gas reaches your eyes and reacts with water to form sulfuric acid—your tears try to wash it away!

Your eyes are allergic to onions — Wrong. It's not an allergy—everyone's eyes react to onion gas. The sulfur compounds form acid on your eyes, triggering a universal protective tear response.

Knife pressure hurts cells — Wrong. Cutting does damage cells, but crying happens because those cells release enzymes that create irritating gas, not from physical cell damage itself.