The Surprising Reason Onions Make You Cry

There are a handful of things in the kitchen that make me fight back some tears. Accidentally grabbing the handle of a skillet that was in a hot oven, nicking the tip of my finger with a vegetable peeler or burning an expensive cut of meat. Pain, frustration and waste are all near the top of my list of kitchen irritants, but there’s one that makes me cry like the opening of the movie Up: cutting onions.

Onions are a component of so many recipes—they can be pickled in vinegar, slow-roasted into melting onions, caramelized with balsamic, grilled and stuffed whole. When cooked, onions turn slightly sweet and have a nutty flavor. Onions are not only versatile and delicious, they are also quite good for you with their ability to improve gut health and heart health. But for all of their positives, onions sure know how to make us tear up. Well, from many, many years of slicing, dicing, chopping, pureeing and mincing onions, I have some tips on how to minimize crying while working with the pungent allium.

Why Do Onions Make You Cry?

In On Food and Cooking: The Science and Lore of the Kitchen, author Harold McGee explains some of the science behind these pungent alliums. He writes, “The distinctive flavors of the onion family come from its defensive use of the element sulfur. The growing plants take up sulfur from the soil and incorporate it into four different kinds of chemical ammunition, which float in the cell fluids while their enzyme trigger is held separately in a storage vacuole.” (A vacuole is a space within a cell.)

Interrupting the cells of an onion—via chopping, slicing and chewing—releases the enzyme that “breaks the ammunition molecules in half to produce irritating, strong-smelling sulfurous molecules,” McGee writes. Onions, in particular, produce a sulfur product that acts as a lacrimator, or a substance that causes tearing: “This volatile chemical escapes from the damaged onion into the air, and lands in the onion cutter’s eyes and nose, where it apparently attacks nerve endings directly, then breaks down into hydrogen sulfide, sulfur dioxide, and sulfuric acid.”

Tips to Reduce Tears

There are many factors that go into the pungency of an onion, including the type of onion, its temperature and age. But just about all onions have the potential to make you cry when cutting them. To minimize the tears, I have some tips to follow.

Use a Sharp Knife

In all my years of working in restaurants and test kitchens, the quickest (and easiest) way to lessen the impact of those tear-inducing irritants is to cut onions with a very sharp knife. This won’t completely eliminate the chance of tearing up a bit when cutting onions, but the more easily you can slice through that allium, the less of the sulfur compounds will float into your eyes.

Try Chilling the Onion

You can decrease the volatile molecules by refrigerating the onions for about one hour. But let’s be honest, there are few situations where I’ll remember to pre-chill onions, aside from prepping a big batch of caramelized onions. I also don’t recommend storing whole onions in the refrigerator long-term, as the excess moisture can turn them mushy.

Work Near a Fan

Keep that sulfur compound away from your eyes and nose with proper ventilation. A basic oven vent won’t really work; instead, you’ll want to turn a fan on and have it blow away from you. This will reduce the amount of lacrimator that enters your nasal passage and eyes.

Protect Your Peepers 

A lot of these recommendations so far help on the margins, but there is one way to keep those tear ducts dry next time you chop an onion. Wear protective goggles and that lacrimator won’t irritate your eyes. Back when I worked in the EatingWell test kitchen, we had a pair of goggles for anyone who wanted to keep their eyes dry. And, despite looking like you’re headed to ski the slopes or swim some laps, onion goggles work great. Even simply wearing glasses (like I do), can help protect your eyes.

The Bottom Line

If you are an allium lover, you don’t have to suffer the tears that come from cutting onions. There are a handful of ways to reduce the high amount of sulfur that’s produced when cutting onions, like chilling the onions or turning on a fan, but the best way to keep your eyes dry is to wear goggles. You can even wear a pair of glasses (aviators when slicing pounds of onions for soup?) to help reduce the tears.