Current DateSeptember 27, 2021

Why we cry when peeling an onion

With a (rare) exception, we all cry when we peel and cut an onion. Impossible to hold back the tears. This phenomenon is linked to a chemical reaction that it is possible to attenuate. Here are the explanations and tips.

On contact with air, the enzyme alliinase and the sulfur contained in the onion form a gas. When this reaches the eyes, and mixes with the tear fluid (water), it causes irritation which is fought by a strong production of tears, in order to dilute the gas.

How to prevent it:

  • Try to breathe through the mouth: the nose is in direct contact with the tear ducts, which do not need an excess of irritant gas.
  • Use a sharp knife, which will release less gas. Rinse it regularly under the tap: the sulfur compounds will react with this water first and lose their strength.
  • When cutting, keep the onion under water, for example under a running tap. The gas will react with water, not the moisture in your eyes.
  • Do not rub your eyes with your hands.
  • Place the onion in the fridge for a few hours or in the freezer for a few minutes before cutting it.
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