In every movie about food, there’s a scene in which the main character—usually an aspiring chef—ends up bawling their eyes out while cutting onions. Anyone with an iota of cooking experience can relate. First the stinging, then the tears—every single time.
Except for maybe a rare few, cutting onions always leads to some kind of crying—watery eyes at best, full-on tears streaming down your face like you just watched a Nicholas Sparks movie at worst. But what’s the science behind it? Are we simply doomed to a life of painful onion encounters, or is there a way to avoid this all-too-common scenario?
Turns out, there are a handful of steps you can take to reduce the tears. SELF spoke to James Chelnis, M.D., assistant professor of ophthalmology at the Icahn School of Medicine at Mount Sinai, about why the sensation happens in the first place, and what you can do to ensure it stops.
When you chop onions, they release a chemical compound that irritates your eyes and triggers your tear glands.
Onions get their distinctive, pungent flavor from sulfur—the same chemical behind rotten eggs’ stinky smell. But 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 is volatile and creates a gas that floats up to your eyes and triggers your lachrymal gland—the gland that produces tears. And that’s when the water works start flowing.
As science-y and scary as that sounds, Dr. Chelnis says that there’s no real danger behind the compound. “It’s just an irritant,” he explains. You could be in a room full of people chopping onions and the worst thing that will happen to you is that you tear a lot. So as painful as cutting onions may be, you’re never going to go blind prepping dinner.
Not everyone will react to the chemical with the same level of intensity.
Ever wonder why your friend can come away from a pile of onions mostly unscathed while you’re reduced to a puddle of tears? No, you aren’t just being extra dramatic. Dr. Chelnis explains that some people have naturally more sensitive lachrymal glands than others. Unfortunately, there’s no way to know ahead of time if you’re extra sensitive or not, and there isn’t much you can do to change it. But there are a few hacks you can use to alleviate the pain.
Try one of these three easy tricks to ward off the weeps.
When an onion is cold, it doesn’t release that chemical compound as easily as it would if it were warm, says Dr. Chelnis. The next time you need to cut an onion, chill it for 10 to 15 minutes beforehand. Better yet, start storing your onions in the fridge—that way you don’t even have to factor in chill time before you get cooking.
Dr. Chelnis also recommends facing a fan toward your chopping station. This will blow the gas away before it has a chance to irritate your eyes.
If you’re really really sensitive to onions, and none of these tricks are, well, doing the trick, try wearing goggles. You may look a little intense, but at least you won’t be crying.