Can Cutting Onions Damage Your Eyes?


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Inquire from the ordinary individual on the sidewalk about the most extensively cultivated crop globally, and they will likely answer with a grain like wheat or rice. After all, these cereal crops consist of the most prevalent staple foods worldwide.

However, while it is true that cereals tend to take a lot of acreage, they cannot compare with the onion for ubiquity. Indeed, the United Nations’ Food and Agricultural Organizations estimates that onions of various varieties and guises are grown in at least 175 countries around the world.

A Brief History of the Onion’s Place in Human Culinary Culture

The National Onion Association estimates that onions became part of the human staple diet in prehistory. It is likely that the first humans began by eating raw onions before the art of cooking and seasoning of food took root.

These pioneering culinary novices must have been the first to notice that the gas the onions release when bitten or cut causes irritation of the eyes and copious tears.

It is safe to presume that the first humans to grow onions did so long before writing was invented. Indeed, references to onions exist in the oldest writings unearthed in the record of human civilizations. For example, vedic writings dating back over five millennia talk of onions grown in the gardens of ancient China.

A bronze age Sumerian cuneiform clay tablet talks of someone assigned the task of plowing an onion patch belonging to the governor of the city.

The hieroglyphs adorning the walls of the great pyramids of Giza include multiple depictions of onions whose meanings do not require an understanding of the ancient script to decipher.

Despite its longevity, the relationship humans have had with the onions over millennia is uneasy, given the bulbous vegetable’s tear-inducing capability.

The onion family has a rich diversity of members ranging from the common red onions to more specialized categories such as green onions and sweet onions.

Depending on how you chop them, all these onion varieties can cause irritation to the eyes. So the question remains: beyond the tears, does the burning sensation caused by onions when they are cut actually cause damage to your eyes?

Before we can answer it, though, it is important first to understand the onion’s kind of plant and how it has developed adaptations to ensure its success as it evolved in the wild.

The Biennial Lifecycle of an Onion

Before the first human ever got teary from chopping onions, the bulbous vegetable had been evolving for millions of years. The onion belongs to a group of flowering plants classified as biennials as they have evolved to grow and reproduce over a two-year lifecycle before they die.

Most biennials experience rapid growth in the first year of their reproductive cycle, storing up nutrients in roots or bulbs beneath the ground. These nutrients are retained and used to spur growth in the second year of the lifecycle when the plant flowers and produces seeds.

Why Chopping Onions Makes You Tear?

A lot of creatures eat up the nutrient-rich bulbs and roots of biennial plants. The plants, in turn, have evolved a variety of defense mechanisms to fend off these freeloaders. The deterrent mechanism onions have taken to is rather ingenious.

As the onions grow underground, they take in ionic sulfur from the soil and use it to make a variety of sulfur compounds known as amino acid sulfoxides.

When you break the outer skin of an onion bulb, the onion secretes the sulfur compounds from its cell walls to make sulfenic acid which then combines with a special onion enzyme in a complicated chemical process to generate syn-propanethial-S-oxide, a gas with irritant properties.

This gas helps deter critters from eating onion bulbs in the soil. This is because when it makes contact with the watery surface of the eye, it turns into sulfuric acid, and the eye tears up in a bid to expel the irritant.

The process by which onions irritate the human eye is well understood. First, the eye’s surface is suffused with sensitive nerves meant to detect any potentially harmful substances that land there.

Then, when these nerves detect the gas formed when onions are cut, they signal for tear glands to secrete tears and get rid of the irritant as fast as possible.

But it is worth noting that the onion developed this defense mechanism to deter burrowing and digging creatures with a penchant for eating raw onion rather than humans who would later learn to use the bulbs to add flavor to their cooked-up dishes.

Indeed, as we will learn shortly, there are ways to avoid the pain when chopping up onions for your dinner.

Is the stinging sensation a signal for damage to your eyes, though? The simple answer is no. The sulfur compounds generated when you cut onions pose just mild and temporary irritation enough to cause your eyes to produce tears but pose no lasting eye health risks.

The irritation normally disappears after a couple of minutes. However, some people with very sensitive eyes have been observed to experience sensitivity for a few hours even after the sense of irritation has gone.

How to Ease Eye Irritation When Chopping Onions?

Even if onions do not pose a serious threat to the health of your eyes, it doesn’t mean you have to endure the irritation passively. Over time, people have outdone themselves in a bid to find effective solutions to treat this irritation.

As a matter of fact, in the wacky corners of the internet, you are likely to come across some crazy suggestions about how to ease the burning sensation in your eyes, such as chewing gum, sticking your tongue to the roof of your mouth, or even lighting up a candle.

This guide, however, only includes proven remedies you can use to minimize discomfort, especially if you have sensitive eyes.

That said, you need to keep in mind that this guide is not meant to provide medical advice. So if our remedies do not work, see your VSP network eye doctor without delay.

Your tear glands produce tears because your eyes try to flush away the irritant acid as fast as possible. If you are one of those people with dry eyes which do not tear easily, you can speed up the process of removing the irritation by giving your eyes a soothing eye rinse using clean water.

The regular eye drops used to treat dry eyes can also offer some quick relief mildly. If you are using both cool water and eye drops to seek relief from onion juice irritation, be sure to rinse the eyes with the cold water before using the drops.

Tips to Avoid Tearing When You Chop Onions

Even better than treating the irritation caused when your eyes react to the gas exposure experience of cutting onions is to prevent it in the first place. Here are some tried and proven tips on how you do just that.

Soak the Onions in Water Before Cutting

This could be the easiest life hack you have ever come across. Dip your onions in water, and you will never again feel your eyes burn as you chop them up. Remember to peel off the dry outer skin and cut off the ends of the onions on a cutting board before placing them in water.

Chill the Onions Before Cutting

It is just as effective as soaking onions in water by chilling them briefly in your refrigerator by running very cold water on the surface before chopping them up.

Cooling the onions condenses the volatile chemicals in their cells, making the aforementioned complex chemical reaction impossible.

Use a Sharp Knife to Cut the Onions

Onions evolved to produce the irritating sensation to ward off critters that gnaw at the bulbs. Gnawing tends to crush into the cell walls, squirting the sulfur compound volatiles which your eyes try to flush with tears.

Using a very sharp knife to cut your onions reduces the amount of damage done to individual cells, limiting the production of volatile compounds and hence the irritant gas that is formed when you use a blunt edge.

Wear a Barrier for Your Eyes

You do not have to prevent the gas that is formed when onions are cut to avoid tears. A more practical way to prevent irritation and tears is to put on a barrier for your eyes. Then, you can wear kitchen goggles or even swimming goggles and enjoy a tearless onion chopping session.

Dice the Onions Instead of Chopping Them

Dicing is a more refined approach to cutting onions rather than chopping them. First, cut the onion bulbs in half by running your knife through from the root to the flower end.

Next, peel off the skin and follow the natural contours of the onion to slice through almost from the flower to the root end. Then, with your knife parallel to the cutting board, make horizontal cuts without cutting the entire way through the half bulbs.

Finish off by cutting the onions vertically, perpendicular to the cuts you first made and running your knife right through to give a perfect dice. This approach leaves a lot more membranes intact and causes less tearing.

Of course, dicing works best for bulbous onions such as red onions but not as well for tuber-like varieties such as leeks.

The onion may look unremarkable and boring crop and culinary ingredients. But as our winding account serves to show, those bulbous tear-jerkers are anything but.

They have been part not only of our diet but also our history, folklore, and myths from as far back as historical records exist.

Given all that you have learned, that teary reaction onions induce when you prepare them should not begrudge them of your respect, if not outright veneration.

But, of course, you do not have to fear that the stinging sensation caused by onions will result in any damage to your eyes. Moreover, we have provided you with enough hacks and tips to ensure you avoid it altogether.








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