Why Do You Cry When You Cut Onions

Why does slicing onions brand you cry?

Slicing onions tin can cause your eyes to tear upward. (Image credit: angelsimon via Getty Images)

Whether sautéed, grilled, caramelized or raw, onions are a staple in many U.S. households; the average American consumes twenty pounds (9 kilograms) of onions per year . Merely their coveted flavor comes at a cost: Whoever chops them may presently experience tears running from their burning eyes. But why does slicing onions brand you cry?

The culprit is chosen the lachrymatory factor, a chemic that irritates the eyes . When the onion is intact, a group of compounds chosen cysteine sulfoxides are kept dissever from an enzyme called alliinase. Simply when you slice, dice or beat out the onion, the barrier separating the compounds and enzyme is broken. The 2 come together, setting off a reaction: The alliinase causes the cysteine sulfoxides to become sulfenic acid.

"Sulfenic acids are non very stable," and so they must change into something else, said Josie Silvaroli, a doc of pharmacy doctoral candidate at The Ohio State University and first author of a 2017 study in the American Chemical Order'due south journal ACS Chemical Biological science most the lachrymatory factor. In an onion, the sulfenic acid has 2 options. Option one is that it tin spontaneously condense, a reaction within itself, and go an organosulfur compound. Organosulfur compounds are what give onions their strong smell and flavor. A similar reaction happens in garlic, which is why it also has such a pungent season, Silvaroli said.

Only choice 2 for the sulfenic acid is unique to onions and a couple other alliums, or a genus of flowering plants that produce vegetables such every bit onions, garlic, scallions and shallots. Another enzyme, chosen lachrymatory factor synthase, that's been hiding out in the cell comes into play and rearranges sulfenic acid into the lachrymatory cistron.

The lachrymatory factor is a volatile liquid, pregnant information technology turns to vapor very chop-chop, Silvaroli said. That's how information technology reaches your eyes and irritates sensory fretfulness. "Your optics start tearing up to get rid of the irritant," Silvaroli told Live Scientific discipline.

It's likely that both the organosulfur compounds that give onions their intense season and the tear-inducing lachrymatory factor evolved as defense mechanisms, Silvaroli said. They are meant to stop insects, animals or parasites that might damage the onion plant.

If burning tears are more than you can bear, you practice take options. Bon Appetit recommends you wearable goggles or a confront shield to protect your eyes. (Contact lenses besides offer a barrier against lachrymatory factor.) Using a sharp pocketknife, which damages fewer cells and creates less "tear gas" than a dull knife, may also help.

There are too efforts to create tear-gratis (or at least fewer-tear) onions. The Sunion , whose cultivators describe it as "sweet and mild," was developed using crossbreeding techniques to be less pungent. But Silvaroli is wary; because the compounds responsible for lachrymatory gene are the same flavorful organosulfur compounds that give onions their singled-out taste, reducing the cry gene could also tedious the onion's flavor. For now, Silvaroli said, "If you lot want that flavour, you might demand to suffer through some burning."

Originally published on Live Science.

Donavyn Coffey is a Kentucky-based health and environment journalist reporting on healthcare, food systems and anything you tin CRISPR. Her work has appeared in Scientific American, Wired UK, Pop Scientific discipline and Youth Today, among others. Donavyn was a Fulbright Fellow to Kingdom of denmark where she studied molecular nutrition and food policy. She holds a bachelor's caste in biotechnology from the University of Kentucky and primary'south degrees in food technology from Aarhus University and journalism from New York University.