Why Onions Make Us Cry: What Science Says

Bylim Olena

Why Onions Make Us Cry: What Science Says
Onions cause lacrimation

At first glance, onions seem like a harmless vegetable. However, when we cut it, tears appear, burning in the eyes, and a runny nose. This is not just an emotional reaction, but the result of a chemical attack that the onion uses to defend itself.

In 2010, chemist Eric Block explained that onions use chemicals to defend themselves against animals that might eat them. When we cut an onion, its cells are damaged, which triggers a cascade of chemical reactions.

How onions make us cry:

Amino acid: The amino acid S-1-propenyl-L-cysteine sulfoxide is released from damaged cells.

Reaction with water: This amino acid reacts with water and enzymes to form 1-propenylsulfenic acid.

Propanethial S-oxide: 1-propenylsulfenic acid decomposes to propanethial S-oxide gas.

Sulfuric acid: Propanethial S-oxide reacts with water to form sulfuric acid. Sulfuric acid irritates the cornea, which causes reflex tears.

How to cut onions without tears

Professor Block, a renowned chemist, reveals the secret of the solubility of the chemical responsible for our tears. This molecule goes into the gas phase very quickly, dissolves easily in water, and is known for its ability to induce tears. So, if you want to avoid this effect, Block recommends some simple tips.

First, cool the onion before slicing, this will help reduce its "volatility." Alternatively, using a range hood to remove steam or chopping onions under water can also be effective methods.

While there are more inventive methods, such as slicing onions under water or with a match between your teeth, they unfortunately don't work very well.

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