Everyone knows that you can expect waterworks when you peel and onion, but why has remained a largely unanswered question……until now. When you cut into an onion, you break open its cells, releasing sulfur compounds in the process. Those compounds quickly become a gas that gets into your eyes and makes you miserable. When the gas combines with the lubricating tears in your eyes, a sulfuric acid is formed, which irritates your eyes and causes pain. This uncomfortable situation kicks your eyes into full-on protection mode. How do your eyes protect themselves? You guessed it: by pumping out tears. Your eyes reflexively tear up to wash away what’s irritating to them. In this case, it’s the sulfuric acid. However, that’s not the whole story. As it turns out, there’s another scientific reason for the tears. The droplets splash upward into the air when the onion tissue is compressed. As a knife compresses the outer skin of the onion, the underlying soft mesophyll is squeezed. When the skin ruptures, the compressed liquid creates droplets that can splash high up into the air, making them more likely to land in your eyes. It’s not just how sensitive your eyes are on any given day or how fresh the onions are. It’s all about the knife you’re using. The study found that blunt knives cause more droplets to form, while a sharp knife reduces tissue compression and droplet spray. Does anything work to reduce the tears? Unfortunately, all those hacks you’ve heard about do nothing. From running onions under cold water and chilling them in the refrigerator to putting a match in your mouth, none of those supposed hacks really works. The best thing you can do is find the sharpest knife you can and wear safety glasses to protect your eyes from the irritating gas.
