How to Cut Onions Without Crying

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By Ashley Woodward • Last Updated: February 16, 2023 is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

How to Cut Onions Without Crying

Tears often seem inexplicable. We cry over the slightest of things, but then sometimes don’t when we really should. Human tear ducts are clearly linked to the emotions – the convolutions of why humans cry are actually fascinating.

But sometimes, tears are far more straightforward. When the wind blows fiercely into our faces, for example, or when we are cutting onions. (Don’t cry dear, it’s only an onion!)

Of course our tears when cutting onions are not emotional – at least, I don’t know anyone who would cry over cutting up a vegetable.

Meat might be a different matter, but onions? No, no tears cried over the cruel treatment of an onion – not that I know of. 

So why does cutting onions make us cry?


Onions bring tears to our eyes due to a chemical reaction. This reaction is caused when two substances inside the onions cells combine. A molecule called sulfenic acid precursor floats around the watery filler of an intact onion cell. Also floating in the cytoplasm you will find little cells called vacuoles. These vacuoles contain a protein called alliinase.


The sulfenic acid precursor and the alliinase will not combine as long as the cells in the onion are not damaged.

As soon as cellular damage occurs, however, those two get together and boy, what a team.

They fit together perfectly, the chemical structure of the molecules changes and the result is a gas similar to tear gas. This new chemical is known as lachrymatory factor. Once it hits your eyes, and gets to the sensory nerves in there, the tears will start flowing.

It turns out, this is not a coincidence.

Lachrymatory factor basically evolved in onions (and a couple of other, much less common plants) as a defence mechanism. Nature is amazing! 

Onions somehow evolved in this way to discourage damage by microbes and animals like us. Weird as it may sound, onions are armed.

Unfortunately for the onions, we put up with the tears in order to get the delicious onion taste that is so useful in so many vegan recipes. What is more, now we have a better understanding of the mechanism and what causes it, we can take some measures to reduce the impact on our eyes of this stingy gas.


If you are one of the people worse affected by lachrymatory factor released when you cut onions then you may be interested to hear that it is possible to reduce, though not completely do away with, the problem.

Below, we outline some of the common methods often described as ways to help you cut onions without crying.

Unfortunately, anything you do to the onions before you cut them will change their flavor.

It is up to you whether or not you are prepared to sacrifice some of the flavor in order to avoid tears and stingy eyes. 

If you are not, your only option is to wear some eye protection while cutting onions – or to get someone else to cut them for you!

Make your own mind up on whether you consider cutting onions to be enough of a problem for you to use one of the solutions (at least partial solutions) described below:


If you cool down your onions before you cut them, you will slow the rate of the chemical reaction within the onions, thereby reducing the quantity of ‘tear gas’ ejected. This will definitely help to reduce the impact on your eyes but unfortunately, it will also change (some say impair) the flavor. 

Whether or not you personally consider it to be a problem, the taste of the onions will have altered somewhat.


Why are you making me cry?

Quickly placing onions in the freezer before you cut them can cause a more dramatic cooling and slow the rate of reaction even more.

Unfortunately, again, this will alter the flavor of your onions and, if you leave them too long in the freezer, can also make them harder to cut, meaning that you have to spend longer cutting them up and may be more likely to expose your eyes to the gas.


A third way to cool onions (and slow the rate of reaction) is to place onions under cold tap water before cutting. Some people even go so far as to fill a basin of water and cut onions beneath the water. Under water, the gas released does become less potent.

Yet again, however, you will lose at least some of that onion taste, since by impairing the reaction process that creates the gas, you are also impairing the processes that produce the taste.


Another method used to impair the reaction is to microwave a whole onion for few seconds before you cut it.

This will indeed impair the reaction to a degree, though, yet again, it can also seriously impair the flavor of the onion in the final dish, so is only one to try if you are getting desperate, have a lot of onions to chop and very sensitive eyes.


There are a number of different theories as to what you can put in your mouth while chopping onions to reduce the impact of the gas on your eyes. Some people swear that putting a matchstick or a piece of bread in your mouth will help, as the match head or bread will absorb the sulphuric compounds before they can reach your eyes.

Does this work?

We’ll leave you to do your own experiments and draw your own conclusions.


Science backs up the idea that using a knife that is as sharp as possible will reduce the amount of lachrymatory factor released, since it will reduce the number of onion cells that are damaged with each cut.

A blunt knife will crush far more cells, rather than slicing cleanly through. So, sharper knife means fewer tears – unless you cut yourself, so be careful!


For some recipes, the hint of lemon or vinegar left on the onions when you chop them using this method will not matter, while for others it may taste rather odd.

If you do not mind the change in flavor in your meal then lemon or vinegar can neutralize the compounds formed in the chemical reaction when cells are broken.

Some wear by this method, while others consider it to be a waste of good ingredients that can spoil the flavor of a finished dish.


Some swear that since the highest concentration of lachrymatory factor is produced in the area by the roots, you should leave this part intact and carefully cut round it. While the tear-producing gas will still be released, however, by the rest of the onion, most people find that their eyes will still tear up.


After a certain stage, most people reconcile themselves to the fact of life that onions will make you cry. But that does not mean that you should not do what is possible to reduce that impact.

Note About Cutting Onions

One simple way to reduce the amount of gas that gets into your eyes is simply to use a cooker hood’s extractor fan, or another fan, or even an open window, to create an airflow and draw the gases away from your face.


The only sure-fire way to prevent onions from making you cry is to cover your eyes properly until all the cutting is done. You will of course look like a complete idiot but this will definitely work, as long as seals around your eyes are intact.

Dude, really?!

You can buy purpose-made onion goggles, though swimming goggles work just as well if you happen to have some of those.

The only other definite way to completely avoid onion tears is, as mentioned earlier, to get someone else to chop onions for you every time you need to do so.


To conclude then, lets take a look at what we are going to do with those onions once we’ve chopped them. Chopped onions can be stored in your fridge in a properly sealed container for a week or ten days.


Some people prefer to put them in water in containers, though this does not really prove to be efficacious in keeping in the flavor from intensifying, as some old wives may have you believe.

It is by far the better option to cut onions as you require them for recipes, or to cook them before you store them. 

If you do decide to get the tears all over and done with in one go then be prepared for a subtle change in flavor and rinse chopped onion before using to remove thiosulfinates on their surface before you use them.

Don’t freeze uncooked onions. You can however store cooked onions in sealed containers for round a year or longer, so this could be a better option if you really cannot bear the tears of chopping onions more often than strictly necessary.


Due to a chemical reaction, onions will make us cry when trying to cut them (in order to make a delicious dinner). There are, however, a couple of ways, more or less efficient, we can minimize it’s influence. Sharp knives and onion goggles will probably only reduce dropping tears. So, the safest way to get rid of tears is to let somebody else do the job for you.

Nevertheless, this is the burden we have to bear in order to eat delicious and healthy lunch. Onions are loaded with numerous health benefits and our allies in fight against diseases, so don’t hesitate and enjoy them mouth full!

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