Why Do Onion Makes you Cry?
Why do onions make you cry?Cutting an onion damages its cells and triggers a chemical reaction that produces an irritating gas. When this gas reaches your eyes, it stimulates sensory nerves, causing your eyes to produce tears to wash away the irritant. In short, your tears are your eyes’ natural defense mechanism against the chemicals released by the onion.
Why Do Onions Make You Cry?
Cutting an onion can turn an ordinary kitchen task into a surprisingly emotional experience. But those tears have nothing to do with sadness.
They are actually your eyes’ natural defense mechanism against an irritating chemical released by the onion.
When an onion is growing, its cells safely store different chemical compounds in separate compartments. This keeps them from reacting with one another. But when you cut, chop, or crush an onion, its cells are damaged and their contents mix together.
One important enzyme released from the damaged cells is called alliinase. It reacts with sulfur-containing compounds known as amino acid sulfoxides. This reaction eventually produces a highly irritating, volatile chemical called syn-propanethial-S-oxide, commonly known as the onion’s lachrymatory factor.
Because this chemical is volatile, it quickly escapes into the air. As you cut the onion, the gas travels upward and reaches your eyes.
Your eyes have a protective system designed to detect irritants. When the onion gas reaches the surface of your eyes, it stimulates sensory nerves, particularly branches of the trigeminal nerve. Your brain interprets this irritation as something that needs to be removed. The result is an increased production of tears.
These tears spread across the surface of your eyes and help dilute and wash away the irritating substance. In other words, your eyes are not crying because onions are making you sad—they are trying to protect themselves.
The amount of tearing can vary depending on the onion, how it is cut, ventilation, and even how sharp your knife is. A dull knife tends to crush more onion cells, potentially releasing more irritating compounds.
There are several ways to reduce the tears. Chilling an onion before cutting can slow the release and movement of its volatile compounds. Using a sharp knife can also reduce unnecessary cell damage. Good ventilation or a fan can help move the gas away from your face.
Interestingly, scientists have also developed onions with much lower levels of the compounds responsible for triggering tears.
So the next time your eyes water while preparing dinner, remember: the onion isn’t making you emotional—your eyes are simply defending themselves.
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