There are two universal truths about onions: They add depth of flavor to a variety of dishes, and they make you cry when you cut them. Both have the same root cause — volatile sulfur compounds. These organic molecules provide the pungent flavor we love, and also the tears we could do without.
Chemists have identified the chemical compound in question, a lachrymatory factor called syn-propanethial-S-oxide. That’s Ph.D.-speak for “a substance that makes you cry.” If you’d rather avoid the runny mascara and nose-blowing, however, here are three proven ways to cut onions without shedding any tears.
Use a Really Sharp Knife
Onions aren’t a tear gas bomb when they’re intact. It’s only when they’re chopped that an enzyme, normally trapped inside the cell walls, interacts with one of those sulfur compounds to make the infamous lachrymatory factor. The more cells are crushed or damaged, the more this enzyme is released, and the more you’ll cry.
So, how do you cut an onion with minimal cellular damage? Use a really sharp knife. A sharp blade shears the cell walls neatly, with minimal damage. A dull one crushes them. That makes a significant difference.
Chill the Onion Before You Cut It
This trick makes the rounds on social media on a regular basis. And unlike many other common onion-cutting hacks, this one actually works. Low temperatures reduce enzyme activity and sulfur volatility, but chilling your onions enough to make a difference takes about 30 minutes in the freezer. Alternatively, store a few onions in your fridge so they’re thoroughly chilled whenever you need to cut them. If the onion isn’t cold all the way through, the hack won’t work.
Cut Onions in Front of a Fan
This onion-cutting hack is also effective, though finding space can be problematic in small kitchens. The onion chemicals won’t irritate your eyes if they never reach them, so put a small fan beside your cutting board. (We like the Fanion, which is adorably onion-shaped and compact enough to sit on your cutting board, but any desk fan will do.)
As you cut the onion, it releases its chemicals in the form of tiny droplets. The fan simply blows them away from you, rather than letting them rise naturally. If you have a powerful vent hood, slicing onions next to the stove with the vent hood running can also help. It’s not as effective as a fan blowing directly across your cutting board, though.
Bonus Hack: Wear Eye Protection
Physically blocking the “onion juice” from your eyes is the ultimate answer. Jobsite-style protective eyewear helps, but swimming or laboratory goggles are better. You may feel foolish, but at least you won’t cry.
