It’s a struggle we all face: onion eyes.
Chopping an onion comes with an extra layer of struggle. After your first few draws through the bulb, your eyes may begin to water, burn, maybe even swell a little. What can you do?
First, let’s understand why this is happening.
Onions are made of thousands of little cells—just like us! In each cell are enzymes, and when we cut into those cells, the enzymes are released and left to mix with sulfenic acids (onions are high in sulfur and amino acids that sometimes mix). When the enzymes and sulfenic acids meet, they form a chemical that vaporizes and finds its way into your sensitive eyeballs. Of course, we don’t just cut an onion once. We cut it over and over and over, causing this reaction every time.
Now, what can you do about it?
In the short term, there are lots of tricks and we’ve heard them all: wear goggles (sure, that might help), soak the onion in water before cutting, chill the onion in the freezer first. We can’t speak to most of these, but we do know one way to relieve the symptoms once they’ve started: open your freezer and place your face as close to the cold air as you can. This cold air will help your eyes feel better quickly, at least until you go back and finish your prep.
What can you actually do about it?
This is an easy answer: sharpen your knives and keep them sharp. The sharper the knife, the cleaner the cut. This is why sharper knives are actually safer to use over dull knives. You may cut yourself either way, but with a sharp knife, the cut will be cleaner with less jagged edges, but it will have less force behind it, since the sharp edge will glide through the food with less pressure than you would need with a dull knife.
With a sharp knife, you are doing less damage to the cells of the onion, which means less of those volatile compounds we don’t like. So, if you sharpen your knife and regularly hone it in between, you will find yourself enjoying your prep just a little bit more.
