Thanks Jason for your tip!
It’s not just the sulfur that’s making you cry. Onions also contain an enzyme called synthase. When you cut into an onion, the synthase reacts with the sulfur to create a chemical compound called syn-Propanethial S-oxide. This compound creates a gas that floats up to your eyes and triggers your lachrymal gland—the gland that produces tears. Some people’s lachrymal glands are more sensitive than others, which is why some people will cry a lot or a little when chopping onions.
Chilling the onion also reduces the gas emitted from this chemical compound. Place the onion in your fridge for 10-15mins before cutting.
If you are still very sensitive – goggles are a sure bet.