science behind onion tears


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science behind onion tears

Tears streaming down our faces while chopping onions have puzzled us for centuries. Though common, the science behind this remains a mystery. What causes it? Why do some cry more than others? Let’s dive into the fascinating world of onion tears!

Onions contain a compound called syn-propanethial-S-oxide (C9H16OS2). It is released when onion cells are damaged from cutting. This compound reacts with our eye moisture and forms sulfuric acid, stimulating our tear ducts. The stronger the onion, the higher its concentration of syn-propanethial-S-oxide, and the stronger the tears.

Some people don’t cry. This is because of genetics. Some have a gene that makes them less reactive to syn-propanethial-S-oxide. To reduce tears, chill the onion before cutting, or wear protective eyewear.

Did you know? During ancient Egypt’s construction of the Great Pyramids of Giza, workers ate onions due to their high nutritional value. They wept while peeling and consuming them. Little did they know they were paying tribute to the science of onion tears!

The Chemistry of Onion Tears

Do you know about the chemistry of onion tears? It’s really something special! Onions produce a gas that, when combined with water in our eyes, forms an acid. This acid can cause a burning sensation and watery eyes. It’s a fascinating chemical reaction!

The Science Behind Onion Tears

Onion tears are a mystifying event that has left scientists wondering for years. What causes them? It’s the onion’s particular components. Let’s check out the table below and discover the science of onion tears.

Lachrymatory-factor synthase
Eye Irritation

Syn-propanethial-S-oxide is released when an onion is cut or squished. It spreads into the air and touches our eyes. This sets off a chain of biochemical reactions, stimulating our tear glands to produce tears as a safeguard.

Lachrymatory factor synthase is another essential element. It converts sulfoxides, found in onions, to sulfenic acids. The acids then become syn-propanethial-S-oxide. This amplifies the release of tears.

Eye irritation is also a key factor in understanding onion tears. Our eyes have special receptors which detect irritants such as syn-propanethial-S-oxide. When they sense it, they send signals to the brain, leading to increased tear production to flush out the irritant.

Surprisingly, a study in the Journal of Agricultural and Food Chemistry found that chilling onions before cutting can reduce the amount of syn-propanethial-S-oxide. This reduces tear-inducing vapors.

Now that we understand the science behind onion tears, we can marvel at nature’s complexity. Next time you’re chopping onions, be sure to keep this knowledge in mind.

Coping with Onion Tears

Chill onions in the fridge for 30 minutes to reduce irritating chemicals.

Cut near running water to dissipate onion fumes.

Use a sharp knife to damage fewer cells.

Slice onions near open flame or hot stove for less sulfur compounds.

Wear protective eyewear to shield eyes from fumes.

Get a chopper or food processor for tear-free cutting.

Sulfur compounds in onions cause tears. Arm yourself with strategies to cope. Enjoy onion dishes without fear. Goodbye tears, hello tasty recipes!

Application in Other Fields

Onion tears have various uses beyond the kitchen. Let’s check out some of them!

Agriculture can benefit by using compounds in onion tears to increase seed germination and healthier plants.

The medical field is researching natural remedies for eye ailments from onion tears.

Cosmetics also use substances derived from onions to ensure products are safe for consumers.

Psychologists use onion tears as a therapeutic tool in counselling sessions.

For full use of onion tear research, scientists, farmers, medical researchers, cosmetic experts, and psychologists must collaborate. They can discover new applications and develop solutions for various industries worldwide.


The science behind onion tears has been captivating researchers for years. We uncovered why onions make us cry – a volatile chemical, syn-propanethial-S-oxide, reacts with our eye moisture and forms sulfuric acid. It is this acid that irritates our eyes and causes tear production.

Cutting an onion has a big part in this process. Damaging the cells releases enzymes which interact with amino acids, forming the syn-propanethial-S-oxide. The pungency of an onion depends on the type and how it was grown.

What’s the big deal? Scientists can develop new techniques or modified onions to reduce tear-inducing effects. No more crying when cooking! Keep exploring the fascinating science world and stay tuned for future onion tech advancements.

Frequently Asked Questions

FAQs – Science Behind Onion Tears

1. Why do onions make us cry?

When we cut an onion, it releases a chemical called syn-propanethial-S-oxide. When this chemical comes in contact with our eyes, it forms sulfuric acid, irritating the eyes and causing them to tear up.

2. Can we avoid tearing up while cutting onions?

Yes, several methods can help reduce tears while cutting onions. These include refrigerating the onion before cutting, cutting the onion under running water, wearing goggles, or using a sharp knife to minimize damage to onion cells.

3. Why doesn’t everyone cry while cutting onions?

The ability to tear up while cutting onions varies among individuals. It depends on the sensitivity of their eyes, the production of tears, and the amount of syn-propanethial-S-oxide released by the onion. Some people may tear up more easily than others.

4. Are there any health benefits to onion tears?

While tearing up from onions may be uncomfortable, it does have a positive side effect. The tears produced during onion cutting contain natural enzymes that help cleanse and moisturize the eyes, offering temporary relief from dryness or irritation.

5. Can onions be modified to reduce tear-inducing compounds?

Research is being conducted to develop tearless onions by genetically modifying them to reduce the production of syn-propanethial-S-oxide or to alter the chemical composition. However, these tearless onions are not yet widely available for commercial use.

6. What are some alternative methods to cut onions without tears?

If tearing up while cutting onions is a major concern, you can try using a food processor to chop onions or opting for pre-cut or frozen onions. These alternatives minimize the exposure to the tear-inducing compounds, reducing the chances of tearing up.

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