QUESTION: How do I stop my eyes from watering when I chop my onions?
ANSWER: The reason onions go from inert globe in the pantry to tear-inducing kitchen assailant is that enzymes and natural compounds in the onion cells, normally kept separate, react with each other to form sulfenic acid. This is unstable so it rearranges itself into Syn-propanethial-S-oxide. The eyes don’t like this, and so release tears.
Scuba mask or swim goggles will block the compound but are uncomfortable and slightly Daliesque. It is airborne so you can try to keep it out of the eyes by blowing it away with a strong fan directed at the face. Slightly Bee Geesesque. This chemical reaction is slowed down at lower temperatures, so chilling an onion for several hours or so before cutting it reduces the effect on the eyes.