The chemical weapons broadly termed tear gas are officially classified as “lachrymatory agents” because they result in tears—along with nausea, burning sensations, watering eyes and a feeling of breathing difficulty.

“And as my lungs, eyes and nose burned with the pain of the lachrymatory agent released from multiple capsules that had fallen around me, I started cursing.”

Onions make us teary because a reaction in the onion releases a chemical called lachrymatory factor, or LF, that irritates our eyes.

"What he was proposing to use in Mesopotamia was lachrymatory gas, which is essentially tear gas, not mustard gas."

So in theory, if you block the lachrymatory factor synthase, you can increase thiosulfinate, and end up with a tearless, yet more tasty, onion!