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Why Do Onions Make You Cry

For those of you who are fans of cooking and being in the kitchen, you’ve likely spent time chopping vegetables, some of which may include onions. If so, you’ve probably noticed that shortly after you cut into the onion, your eyes begin to burn and swell with tears.

This is not only annoying but can also be painful, making it hard to complete the cooking task.

So, what’s the real reason why onions make you cry? Keep reading to learn all about this universal phenomenon and even some ways to help reduce the pain and prevent this problem from occurring.

why do onions make you cry

Why Do Onions Make You Cry: A Scientific Explanation

There is a (sort of) simple scientific explanation behind the question, ‘Why do onions make you cry’, and it all boils down to chemistry and biology. Because onions mature underground, they’re often prematurely eaten by underground critters that generally feast on roots and bulbs.

As a form of protection, onions naturally produce enzymes and acidic chemicals released when the vegetable’s skin is broken to shoo off unwanted foragers.

The combination of enzymes and acids (specifically sulfenic acid) produces an irritating gas known as propanethial S-oxide. This gas stimulates the formation of tears when it reaches the eye.

Once the acidic compound touches the layer of tears that protects the eyeball, it turns into sulfuric acid. This sulfuric acid triggers the eye to flush it out with the production of more tears, which explains why onions make you cry.

How to Prevent Crying

sliced white onion

Now that you know the answer to the age old question that asks ‘why do onions make you cry?’, you may be wondering, ‘what now?’.

However, tears from onions are a common problem that many people experience, what you really want to know is how to prevent or minimize it. Listed below are a few tips that may help you prevent crying in the kitchen when it’s time to cut your onions.

Proper Cutting Techniques

There are a few ways of cutting your onion that may help prevent or reduce crying. It’s recommended that you should not cut from the side closest to the root end of the onion. This is because that area has the highest concentration of sulfuric acids and other compounds that contribute to the crying.

It’s also suggested that you slice the onion facing away from you so the chemicals don’t directly release into your eyes.

Also, make sure you’re always using the sharpest knife available. A sharper knife allows for cleaner cuts and therefore less damage to the onion (and less exposure for chemicals to be released into the air)


Many people have benefitted from wearing eye protection to help prevent onions from making you cry. Whether you use eyeglasses, sunglasses, or goggles, the protection from these materials may help block and reduce the amount of acid that reaches your tear ducts and decrease your tear production.

It may also help to work near a cooking hood with ventilation or have a fan blowing nearby to decrease the ability for the chemicals to reach your eyes and reduce the ability for onions to make you cry.

Using Water

Placing your onion in a bowl of cold water, fully submerged, may help to diminish the amount of sulfuric acid found within the vegetable. Make sure that after you remove it from the water you fully dry your onion so that it doesn’t splash and split apart when added to your cooking pan.

It has also been said that running water or placing a wet paper towel near the edge of your cutting board can help attract the irritating molecules away from your eyes and towards these water sources. This has never been scientifically confirmed, but it can’t hurt to try!

Onion Alternatives

Bowl with dried onion powder.

If, still, onions are making you cry, and none of these prevention techniques work for you, luckily there are some alternatives you can use when cooking to swap out that pesky onion.

Onion Powder

If the dish you’re cooking requires an onion simply for its flavors, try using onion powder instead. This can be easily found at any grocery store or market and makes for a quick and painless alternative to onions and ensures your recipe has all the flavor it needs, without the hassle.


If onions make you cry but you love the taste of caramelized onions, a great alternative is fennel. Interestingly enough, cooking with fennel provides a similar flavor profile to that of a caramelized onion. When raw, it has a flavor like black licorice, so make sure to cook it before you use it.

Fennel is a perfect addition to soups and is the ideal substitute when you’re not in the mood for onions making you cry

Other Alliums

Onions, along with other cooking ingredients, fall under the plant genus Allium. Luckily, not all members of the allium genus make you cry.

For example, garlic, shallots, leeks, and scallions are similar to onions, but they don’t carry the same compounds that are found in these vegetables, and therefore won’t leave having to wipe tears away while chopping.

Frequently Asked Questions

Plate full of chopped onions with sweet onions, mexican onions and green onions on a white plate on the kitchen table.

Does the type of onion make a difference?

From yellow and white, to red and even green, there are many different types of onions with a variety of flavor profiles used for cooking. However, certain types of onions make you cry more than others.

Types of onions that make you cry more than others are those that have the ability to create the harshest chemical reaction. This is because, again, of their high amount of compounds that contain sulfur. Specifically, red, yellow, and white onions are the most irritating types.

Sweeter onions often cause less issues and tears than those with a stronger flavor. For example, green onions have much less sulfur than others and is likely to help reduce the problem of onions making you cry.

How do I relieve the pain once it has started?

If you’ve dealt with onions making you cry, you’ve probably noticed that the tears aren’t the only result of the chemical reaction. Oftentimes with the tears, your eyes will begin to burn or sting and it’s hard to get rid of. Here are some of our favorite remedies for relieving the pain that comes along with onions making you cry:

Flushing your eyes with cool water is the first step to help relieve the pain that you feel when onions make you cry. Make sure you’ve washed your hands to remove any remaining sulfur or acid, and ensure you’re also using clean water.

Eye drops and artificial tears are another way to help flush the chemicals that are irritating your eye. The lubrication from these drops stimulates even more tear production to help relieve the pain.

Some people find relief in using cold compresses on the eyes, such as a wet rag, ice pack, or even chilled cucumbers. Aloe vera gel and wet cotton balls may also help with the pain when onions make you cry.

Now That You Know

So if you’ve always been plagued with this frustration, or you’re simply someone who has been haunted by the question of ‘why do onions make you cry’, hopefully now you have a better understanding of how and why these vegetables cause such trouble.

If you do struggle with tears, hopefully, this article has provided you with some helpful tips and tricks that allow you to continue enjoying the flavors of this unique vegetable, without all the pain.

Curious to learn more about all things onions? Take a look at our Onions post for everything you need to know.