How Not to Cry Like a Baby When Cutting Onions

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Ever wondered why every time you need to slice-up even one measly little onion your eyes immediately start to tear-up? My friends, the struggle is real...but that's not to say that there's nothing that can be done about it.

My name is Jeff Potter, and I'm the author of Cooking for Geeks, a book that takes your passion for food and love of science and marries the two, to reveal the hidden secrets behind the foods you love.

Today's installment will help you to understand why you start to cry like a baby every time you need to slice an onion, and I'll offer a few suggestions to help you cope with any future onion tears that may come your way.

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Step 1: Understanding Onion Tears

Onions make you tear-up because the moment you cut into them, they release a sulphur-containing gas that is very irritating to your eyes.

So…if irritating gas + eyeballs = crying, the goal then is to remove at least some of the irritating gas out of the equation. Because, science.

There are a few ways you can accomplish this.

Step 2: Use the Sharpest Knife in the Drawer

You don't have to be the sharpest knife in the drawer to use the sharpest knife in the drawer….or...so the saying goes.

A sharper knife makes a cleaner incision, thereby tearing less of the flesh of the onion, and thereby releasing less gas.

Step 3: Keep Cool

The sulphur-containing gas released by the onion is created by an enzyme. At cooler temperatures, rates of reaction slow down, leaving a less than optimal environment for the enzyme to work its magic and release the gas.

Step 4: Air It Out

To keep the gases from reaching your eyes, try using a fan to blow the gas away from you. This is especially helpful if you have a lot of onions to cut.

Step 5: Extreme Countermeasures Are Always an Option

If you've done all of these things and you're still struggling, you can always go the full nerd and wear protective eyewear that seals around the edges. Swim goggles work well, as does a snorkelling mask (snorkel optional).

Step 6: Check Out the Book!

You can find this instructable on page 39 of Cooking for Geeks. For more practical tips and tricks like the one you've just witnessed, check out the rest of the book by reading two chapters for free!

If you've enjoyed this information and would like to see more, don't forget to also subscribe to and like my YouTube channel.

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9 Discussions

We have recently been keeping our onions in the fridge, and with my new knife set, I've noticed practically no irritation. Thanks for the scientific reason why!

2 replies

Hurrah! One minor comment: long term storage of onions in the fridge isn't recommended, as it'll lead to mold growth. This may not be a problem if you go through onions quickly enough. Happy cooking!

I cook a LOT so I tend to use them rather quickly. Thanks for the heads up though!

love your commentary!!! plus good onion ideas. let me add what I do.... I don't know chemically if this is good or bad for cooking but it works for me. I slice off the two ends, make one small cut longwise and peel. then, here's the important part, I run the onion under cold water. does the trick and I don't have to store the onions in the fridge - no room. I haven't cried over my onions in years.

3 replies

Running them under water works well too — the compounds that cause tearing up are water soluble, so you are rinsing them away. Technically cutting with a wet knife on a wet cutting board will work too, but that's slippery and thus dangerous.

Running them under water works well too — the compounds that cause tearing up are water soluble, so you are rinsing them away. Technically cutting with a wet knife on a wet cutting board will work too, but that's slippery and thus dangerous.

Running them under water works well too — the compounds that cause tearing up are water soluble, so you are rinsing them away. Technically cutting with a wet knife on a wet cutting board will work too, but that's slippery and thus dangerous.

Nice. Another thing you can do is put your onions in the freezer for about ten minutes before you cut them, living with my family of six, there is never room in our fridge, but usually there is room in the freezer. I actually learned this doing a science experiment with a friend. Been doing it since.