Why Do We Cry When Slicing An Onion?


When an onion is ruptured—such as by a knife—its cells break open and release irritating compounds that form a substance called propanethial sulfoxide, which is similar to sulfuric acid.

English: onion

A non-tearless Onion

As the nerve endings of your eyes’ corneas detect the irritant, your brain tells your eyes to produce tears to wash it away. In other words, all that crying is your body’s way of protecting your eyes. It also seems to help if you block the cornea by wearing goggles.

Using gene silencing technology, Dr. Colin Eady of New Zealand recently developed a so-called tearless onion by shutting down the gene in the vegetable that produces the irksome substance. It’s still in the development stage, however, and there’s no word yet on whether the new onion tastes better or worse than its weepy relative.

The terrifying-sounding science of gene silencing uses RNA interference to shut down specific genes.

By switching off the genes that give onions their sulfur-based eye-watering power, a Dr. Colin Eady and his collaborators in Japan have whipped up what appears to be a tear-proof onion.

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