Why Onions Make Us Cry

Why Onions Make Us Cry

You can fry them, use them as garnish, bake them or use them to give your meal a little texture. They add bold flavors to any dish, but onions are a nightmare to chop. Unless you’ve got eyes made of steel, onions have made you cry at least once.

Why is it that onions make us cry? No, it isn’t a subconscious reaction of feeling sad for the onion. The actual answer is quite scientific.

A Need for Survival

We’ve touched on this subject of survival in the past. Our eyes developed this way not only for the purpose of being able to see, but to give us a survival tool. We have depth perception and can see in color as a result of our survival tool kit. Without it, we wouldn’t be able to foresee potential threats.

The same goes for onions, like any other animals or plant. They are all about survival. Just like a Venus fly trap traps intruders, onions have a different approach to warding off threats. They wage war using chemical warfare.

To prevent predators in the wild (and the kitchen) from eating the onion’s bulbs, it releases chemicals to cause animal’s eyes to well up.

The bulb, which is the part we eat, is the onion in the first year of its life. If it gets to its second year of life, the bulb will produce flowers and seeds as a means of reproducing. Unfortunately, onions are delicious and don’t often make it to their second year of life.

In an attempt to get there however, the onions release these chemicals when bitten into or cut up. Onions make us cry as a means of defending themselves. Most animals would let the onion go, but we are a persistent species.

About the Chemicals

We have long known that the chemicals being released by the onions were some sort of defense mechanism. However, it is only recently that scientists have been able to identify the exact chemicals in the onion. The chemistry is more complex than you’d expect from a simple onion, but that’s what makes it fascinating.

The chemical at the root of our eye discomfort is called lachrymatory factor (LF). Our lacrimal glands are the glands in the eyes that produce tears. LF is a chemical that produces the most tears.

When we cut into an onion, the cells begin to break down and release an enzyme called allinase. This enzyme produces the chemical and releases it into the air. Ironically, the chemicals produced by allinase are also what give the onion its flavor. You can’t have a delicious onion without a little crying.

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How It Affects Our Eyes

Why Onions Make Us Cry

Once the chemicals from the onion are airborne, they waft up right into our eyes. It will first hit our cornea. Our body’s natural reaction will be to blink away this foreign matter. However, once the eyes realize that this is no ordinary foreign matter, they will send messages of distress to the brain.

The brain will then activate the lacrimal glands and before you know it, you’re crying like a baby over a chopped onion. Chopping into an onion doesn’t just affect the eyes. Your nose may also become stuffy or begin to run. Your body is working extra hard to expel this chemical from your body.

The truth is, we don’t actually understand the structure of the enzyme that releases the chemical. LF was only first identified in 2002! Knowing how the enzyme works could lead to better understanding how to prevent tears while cutting onions. Maybe we’ll even be able to grow them sans enzyme one day!

In the meantime, there is a trick to minimize the amount of tears. The root of the onion is the part that releases the most chemicals. Instead of chopping it off right away, keep it on. Chop the rest of the onion first and then the root last.

This won’t guarantee no tears. But, it will definitely reduce it from full of sob-like tears streaming down your face to something a little less dramatic.

Ways to Treat Irritated Eyes

What can you do if you have really sensitive eyes? If you have sensitive eyes, it can be double the trouble to cut onions. If leaving the root on still causes your eyes to react strongly, here are some ways to treat your irritated eyes.

First, give them a break. This is really the easiest way to treat them if time permits. Cut the onion as much as you can until your eyes can’t handle anymore. Then, go outside or stick your face in the fridge. Yes, we’re serious. The cool air will relieve your eyes almost instantly.

However, if you’re working in a fast paced environment like a restaurant kitchen where you may not have time for a break, there are other options. You can try wearing wrap-around goggles.

It may sound silly, but if your eyes are very sensitive to onions, it may be your only option. These googles will prevent the chemicals from entering the eye. Really, chopping an onion is just like dealing with any other chemicals. Perhaps it’s a little less dangerous, but they are chemicals no less.

Another trick is to run the faucet while you chop the onion. Now, there is no science behind this one and it could very well just be a placebo effect kind of situation. People claim that letting the water run while cutting onions doesn’t make them cry! Try it for yourself and let us know how you faired!

Who knew such a little bulb could wreak so much havoc on our eyes? Don’t worry, for all this talk of chemicals, LF is harmless. It’s an irritant more than a chemical that will cause damage.

However, if you do find that you have sensitive eyes (or they are more sensitive than normal), talk to your doctor. Often hidden infections and diseases will make your eyes more sensitive.

Next time you find yourself cutting onions, don’t cry. Just keep calm and leave the root on!

About the Author

Avatar for Tyler Sorensen

Tyler Sorensen is the President and CEO of Rebuild Your Vision. Formerly, Tyler studied Aeronautics with the dreams of becoming an airline pilot, however, after 9/11 his career path changed. After graduating top of his class with a Bachelor of Science degree in Informational Technologies and Administrative Management, he and his brother decided to start Rebuild Your Vision in 2002. With the guidance of many eye care professionals, including Behavioral Optometrists, Optometrists (O.D.), and Ophthalmologists (Eye M.D.), Tyler has spent over a decade studying the inner workings of the eye and conducting research.

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