Why Does Cutting Onions Make Our Eyes Tear? Know The Scientific Reason

Why Cutting Onions Makes Us Cry: We all have experienced it—standing in the kitchen, chopping onions and suddenly tears start rolling down our cheeks as if we are crying for no reason. This is among the most annoying aspects of cooking for a lot of people. However, have you ever wondered why we cry when we see onions? Is it a natural reaction or something dangerous? Science has the answer.

Onions have special compounds that protect them from insects and animals in the wild. These substances are released into the atmosphere when we cut an onion. Our body responds by releasing tears to remove them as soon as they get to our eyes. This is merely a chemical defence mechanism that the onion plant has evolved over thousands of years, not because onions are "bad" for us. The good news is that onions don't damage our eyes; the tears are merely a normal reaction. Let’s understand the process in detail and also explore some easy tricks to avoid it.

The Science Behind Onion Tears

Why cutting onions makes us cry (Image: Canva)

Onions have Sulfur compounds in them that help them grow underground. When we cut an onion, its cells break and release an enzyme called alliinase. The alliinase enzyme reacts with sulfur compounds, producing a gas named syn-Propanethial-S-oxide.

When the gas reaches our eyes, it irritates the surface of the eye and stimulates the tear glands. Our eyes then, naturally, make tears to flush out the eye's irritant. In short, the tears produced are a protective response of our body, not something hazardous.

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Why Do Onions Have This Reaction?

Onions developed this defence mechanism to help them survive. They release these irritating gases to protect themselves from animals, pests, and even microbes. Onions ensure that they are challenging to eat raw in this way. For us, it's just a hassle when we're cooking.

Are Onion Tears Harmful?

Onion gases don't damage human eyes, which is good news. They only irritate you for a short time. The tearing stops on its own when you stop cutting or move away from the onion.

Tips to Avoid Tears While Cutting Onions

Tips to avoid tears while cutting onions (Image: Canva)

Here are some simple tricks you can try in your kitchen:

1. Before chopping, let the onions cool in the fridge. The release of irritating gases is slowed down by cold temperatures.

2. Use a sharp knife – a blunt knife crushes more cells and releases more gas.

3. Cut near running water – water absorbs the gases before they reach your eyes.

4. Wear kitchen goggles if you are cutting large amounts of onions.

5. Cut off the root last, as it contains the highest concentration of tear-inducing compounds.

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Cutting onions can make you cry unexpectedly, but there's a scientific explanation. It is a spontaneous reaction brought on by sulfur compounds that onion cells release. It may irritate you, but it's harmless and easily reduced with a few easy tricks. Keep in mind that it's science at work, not you, the next time you chop onions!