Why Chopping Onions Makes You Cry

Onions are notorious for making us weep, but why? Scientists say they now have a pretty good understanding of what's going on, reports NPR in an interview with chemist and author Eric Block. It turns out the vegetable has "evolved a chemical defense system" in an attempt to get us, not to mention the many creatures living in the ground where onions grow, to stop having our way with them. "The way the onion bulb is designed," Block says, "is ingenious." Each onion cell houses what he calls "a little glob" filled with enzymes, and when cut into, the globs break open and release their innards, setting off a chemical reaction. Resulting molecules released into the air float up—and into our eyes.

The tears come because our eyes are equipped with sensory nerves to protect us from irritants and, for our own defense, produce a burning sensation, explains a video from the American Chemical Society. Tears help wash away such irritants. So what to do? For starters, chop in a well-ventilated area, perhaps near a fan, suggests Block. Refrigerating the onions prior to cutting also can help. Wearing goggles, however, will only make you look stupid, he says, because they won't stop the irritants from getting into your nose and mouth. The Huffington Post debunks some other home remedies, such as putting vinegar on the cutting board, but finds that others, such as chopping the root last, seem to help. (When it comes to heart health, onions may be worth all the tears.)