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Why Cutting Onions Makes Us Tear

January 24, 2009

Ah onions, that bulbous wonder! Available in the can, frozen, powered or pickled, but most commonly chopped or sliced. It's the latter form that always makes one a little teary-eyed just thinking about it. Which brings us to our post topic for the day. Why do onions make us tear?

When onions are sliced, cells are broken which release a gas that diffuses through the air. When this gas reaches the eye it reacts with fluid in the eye to form a diluted solution of sulphuric acid. The nerve-endings in the eye then become irritated, making them sting. Tears are then produced by the tear glands, to help flush out the irritants.

So what can you do to help minimize the tearing while slicing an onion? There are a number of theories or suggestions out there, here's what we've found while researching the topic:

  • Freeze the onion for about 10 minutes and then peel. Freezing the onion reduces the activation of the enzymes that cause the irritating gas to be released.
  • Cut the onion in a basin with water or under running water in the sink. The sulfur gas from the onion will react with the water before hitting the eye thereby reducing eye irritation.
  • Why not try a pair of swim goggles or safety glasses?
  • Try a piece of bread in your mouth. The bread should absorb the gas before reaching the eye.
  • If you have contacts wear them. I even found a post on the web from a cooking instructor who had LASIK and afterwards requested non-prescription contacts to use while she taught, she swears it works.
  • Cut near an open flames (ie. candle) The fumes from the flame will react to the gas being released and help minimize irritation.
  • Using a sharp knife blade will limit cell damage and the amount of gas released that cause eye irritation.
  • While slicing the onion, avoid the root area where the concentration of pungency is found.

We also found this video that shows how to cut an onion without tearing:


Cut An Onion Without Crying 

Whatever method you chose, here's hoping your slicing will be tear-free from now on. Have your own suggestions? We'd love to hear what works for you!! 

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