Why Do Onions Make Us Cry?

Crying over onions is one of the most common kitchen frustrations, but have you ever wondered why onions have this effect on us? Let’s dive into it.

What's Really Happening When You Cut an Onion?

When you slice into an onion, you're breaking open its cells and triggering a chemical reaction. Onions contain sulfur compounds that they've absorbed from the soil as they grow. These compounds are stored separately from certain enzymes within the onion's cells. As long as the onion is whole, everything stays peaceful. But the moment you cut through it, the enzymes and sulfur compounds mix. This mixing creates a volatile gas called syn-propanethial-S-oxide. It's incredibly light and quickly evaporates into the air, floating up toward your face as you're chopping, and makes you tear up.

Why Do Our Eyes React This Way?

Your eyes are incredibly sensitive, and sulfuric acid, even in tiny amounts, irritates them. Your body's immediate response is to flush out the irritant, so your tear glands kick into overdrive, producing tears to wash away the acid and protect your eyes. It's actually a brilliant defense mechanism.

Why Do Onions Do This in the First Place?

In nature, onions are trying to avoid being eaten by insects, animals, and other threats. When something bites or damages the onion, the release of these irritating compounds discourages the attacker from continuing.

Can You Avoid the Tears?

While you can't eliminate the reaction, some tricks help reduce the tears. Chilling onions in the refrigerator before cutting them slows down the enzymes, reducing the amount of gas produced. Cutting onions under running water or near a fan helps disperse the gas before it reaches your eyes. Some people swear by wearing goggles or even swimming goggles while chopping; you could avoid crying. Using a very sharp knife also helps because it damages fewer cells, releasing less of the irritating compound.