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Why Do Onions Make Us Cry?

By Lauren Ford
Posted On Jun 22, 2016
Why Do Onions Make Us Cry?

We’ve all been there, pulling a Risky Business type dance in the kitchen, ready to make a fresh veggie omelet, when you start chopping your onion, and the tears start simultaneously falling. You are in such a great mood, but the onions don’t care.

Why in the world do these lovely veggies cause us grief?

According to Eric Block, who published a book on the science behind onions, it’s because of a chemical irritant called syn-Propanethial-S-oxide. “The onion is a perennial bulb that lives in the ground, with lots of critters looking for a snack. So it has evolved a chemical defense system,” Block said.

Basically, the onion is all of us who are tired of giving everything we’ve got and getting nothing in return. The onion is smart; it’s built up a defense mechanism to ward off bullies and make them cry. Five points for Mrs. Onion.


Block explains, “Within each onion cell, there is a little glob- a sealed vacuole- filled with enzymes. When you bite or cut into an onion, these enzyme-filled blobs break open, releasing their contents, which then mix with other chemicals inside the onion cells.  In an instant, a whole cascade of chemical processes happen, and a bunch of syn-Propanethial-S-oxide molecules form as a result of all those chemicals. These molecules are really tiny and light causing them to float up into the air and into the eyes of the person that’s cutting the onion.“

If you want to avoid a mini cry session during your cooking routine, there are a few ways to get around the onion’s tiny floating chemicals. You can cut the onion with a fan blowing nearby so that the molecules blow away rather than up into your eyes. Also, refrigerating the onions before chopping them might help because the chemicals are less volatile when they are cold. Or you can just rough it out and shed some tears.

I have a new found respect for onions. They don’t take anyone’s BS. If I had a spirit vegetable, like I do a spirit animal, it would surely be the onion.