Plus, proven methods that help to minimalize your tears.

By Kelly Vaughan
February 05, 2020

If you've ever prepared a batch of onion soup, you know that in addition to plenty of sweet onions and sharp knife, a full box of tissues is necessary. Onions cause us to cry, yes, but how and why does this happen? We asked Dr. Alyson Mitchell, professor and food chemist in the Department of Food Science and Technology at UC Davis, to explain the science behind why raw onions make you cry—and what you can do to prevent it.

Related: Why Knife Skills Are So Important

Why Do Onions Make You Cry?

Onions are part of the allium family, which includes garlic, leeks, shallots, and scallions, all of which can absorb sulfur from the soil they grow in. Sulfur can be combined with amino acids to form amino acid sulfoxides, which are stored in plant tissues. "When you cut an onion, you break open the cells in plant tissue exposing the amino acid sulfoxides to enzymes, which convert them into a compound known as lachrymatory factor synthase, which is an irritant. It floats into the air and reacts with the surface on your eyes, so your eyes tear up to flush it out," says Dr. Mitchell. This enzyme is not found in leeks and garlic, which is why you don't cry when you work with them in the kitchen.

Emily Roemer

Old or New Onions—Which Is More Likely to Make You Cry?

"If onions are older, tissues break down with time so you could have leakage of that enzyme into the cellular fluids," says Dr. Mitchell. This means that older onions are more likely to make you cry when chopped. So, how do you tell the difference between new and old onions? When shopping for onions in the grocery store, look for peels that are still intact versus those that look like they're dried and flaking off.

How to Prevent Onions from Making You Cry

Now that you understand the science behind why onions make you cry, you might be wondering if there's anything you can do to avoid the water works? While Dr. Mitchell says there is no scientific evidence that chewing bread or gum works, she does offer some proven methods. Perhaps the easiest option is to keep onions in the refrigerator—"The colder an onion is, the less able it is to release volatile molecules." And always use the sharpest knife possible, which will cause less damage to the onion and therefore, the less of the enzyme will be released. As a last resort, try wearing onion goggles, which act as a barrier between your eye and the enzyme—we like RSVP International's option ($18.91, amazon.com).

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Comments (2)

laura.cionca
February 8, 2020
You might look a little silly but if you put swim goggles on BEFORE you begin slicing the onions you’ll have absolutely no issues. My husband taught me this trick and it works!
aksharif
February 7, 2020
I've always found submerging the onions in water for a few minutes helpful.