Subscribe now

Physics

Physicists reveal the secret to chopping onions without crying

Slicing an onion releases tear-inducing chemicals into the air, but the sharpness of the knife and the speed of the cut can affect how these droplets are expelled

By Alex Wilkins

15 May 2025

Cutting onions can be a tearful experience

Foster.r/Getty Images

If you find yourself crying when chopping onions, physicists have found a possible solution – but professional chefs probably aren’t going to like it.

When onions are cut open, they spray a mixture of sulphur-rich compounds into the air, one of which is syn-propanethial-S-oxide, a chemical that triggers the nerves in the eye responsible for producing tears.

Sunghwan Jung at Cornell University in Ithaca, New York, and his colleagues used a high-speed camera to analyse in detail the spray produced when…

Sign up to our weekly newsletter

Receive a weekly dose of discovery in your inbox! We'll also keep you up to date with New Scientist events and special offers.

Sign up

To continue reading, subscribe today with our introductory offers

Piano Exit Overlay Banner Mobile Piano Exit Overlay Banner Desktop