As a child, you may have wept over each piece of broccoli mom bribed you to eat. Nowadays, you’re proud to admit that veggies don’t make you cringe or cry—except for onions, of course. So why is it that the innocent onion can easily break even the most resilient facade? Because everyone’s wondered at some point or another, we’ve finally stumbled upon the weird scientific reason that explains this.
According to The New York Times, besides cuing the waterworks when you chop, crush, or cut an onion, the veggie releases lachrymatory factor, or LF, a chemical that affects your eyes’ sensory nerves and subsequently causes them to tear up. You’ve probably already noticed, but LF isn’t released when you peel the allium.
So why exactly does this occur? Just like we humans have evolved defense mechanisms to protect us from predators, LF was meant to protect onions from humans, animals, and microbes, which is why piercing through and breaking its cells causes the chemical’s release. Once the onion’s cells are damaged, the onion’s sulfenic acid precursor molecule meets a protein called alliinase and causes the tear gas-like chemical reaction.
Although scientists still don’t know why some onion breeds are more tolerable to us than others, Marcin Golczak, a biochemist at Case Western Reserve, suspects that fresher onions are packed with more LF than their older counterparts, according to The New York Times. While using elder onions might combat their crying effects, some swear by using a sharper knife, which would cause less cell damage and therefore release less irritants. Although none of these hacks are science-backed, we recommend chewing a stick of gum or donning a pair of goggles while chopping onions to prevent the tears. These hacks should come in handy when you’re prepping some of these 20 Best-Ever Fat Burning Soups.