No More Tears? Scientists Take a Keen Eye to Onion Slicing

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Yesou come home from work after a busy day and rush to make dinner. Moments later, you’re reeling from a chemical attack in your own kitchen: onion fumes and a blurry-eyed interruption to the evening’s preparations. It’s a scenario so familiar it seems inevitable, but what if science could help?

While tips for mitigating the tear-inducing effects of chopped onions are plentiful, the science behind them is relatively sparse. We know the chemistry behind why slicing onions causes tears – the sulfur-containing compounds tickle nerves in the cornea – what’s less clear is the physics behind the eruptions of these noxious fumes. Until now.

Publication in the Proceedings of the National Academy of SciencesResearchers at Cornell University have revealed new insights into the mechanisms of onion droplet formation and some practical tips on how to minimize it.

To study the phenomenon, the researchers used a computer model to analyze high-speed images of knives of different sharpness cutting onions at different speeds. They found that “faster or duller blades significantly increase both the number and energy of ejected droplets.” In other words, using a sharp knife and slow slicing can prevent nasty onion spray from reaching your eyes. (Bad news for those of us whose knives and time management skills aren’t as finely honed as they should be.)

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The reason, according to the authors, lies in the structure of the onion itself. The outermost layer of the bulb, just under the papery skin, is relatively stronger than the inner layers. This means that when a dull blade presses, it compacts the spongier mesophyll beneath, producing a more energetic explosion and higher volume of fluids upon release.

So sharp knives and deliberate cuts are your best bet to minimize droplets reaching your eyes, but what about other remedies? Researchers examined whether refrigerating onions reduced droplets, but issued a new caution. They found that cooling the onions actually produced a greater volume of ejected droplets, likely due to the fragility of plant tissues at lower temperatures (although the authors note that more in-depth studies are needed before definitive conclusions can be drawn).

For those wondering why scientists would devote the effort to analyzing diced onions, the applications of their research extend beyond simple meal preparation. Foodborne illnesses can be spread not only through contact with contaminated tissues, but also through aerosolized liquids. “Atomized droplets are perfect carriers of viruses and bacteria,” write the authors, notably Salmonella And Campylobacter. Something to consider the next time you take on slicing without sharpening your knives first.

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Main image: Photoongraphy / Shutterstock

• Jake Currie

  Published on October 29, 2025

  Jake Currie is a writer based in Brooklyn, New York.