Hi Curious Mind,
Imagine this: you’re in the kitchen, ready to chop an onion for dinner.
You lift your knife, slice… and suddenly your eyes sting.
Before you know it, you’re crying like someone just told the saddest story ever.
But it’s not sadness. It’s onion science — and it’s wild. Let’s walk through the story.
The Onion’s Secret Arsenal 🧪
Onions might look innocent, but inside they’re like tiny chemical factories.
They store sulfur-containing compounds, scientifically called S-alk(en)yl-L-cysteine sulfoxides, in separate cells.
Concentration: about 0.1–1% of the onion’s weight.
These compounds are completely harmless… until you attack.
Think of it like this:
“Don’t touch me… or else!”
Slice the onion, and the cells explode. Suddenly, the sulfur compounds are free.
Enter Alliinase — The Enzyme Trigger ⚡
When the cell walls break, the sulfur compounds meet alliinase, an enzyme waiting quietly inside the onion.
Alliinase reacts with the compounds in seconds, creating sulfenic acids.
This reaction is fast enough that your brain doesn’t have a chance to protest.
It’s like the onion saying:
“You broke my defenses. Time for chemical chaos!”
The Tear Gas Appears — Syn-Propanethial-S-oxide 😭
The sulfenic acids don’t stop there. They quickly rearrange into a gas called syn-propanethial-S-oxide.
This is the molecule that makes your eyes water.
Even tiny amounts — micrograms — trigger your trigeminal nerve in your eyes.
It reacts with the water in your eyes, forming a mild sulfuric acid, just enough to make you cry but not harm you.
Your brain goes:
“WARNING! EYES UNDER ATTACK! RELEASE TEARS IMMEDIATELY!”
Result: your tear glands flood your eyes to protect them.
Why You Can’t Escape It 🚫
This tear gas is volatile — it floats up fast.
The closer your eyes are, the faster you cry.
Sharp knives = less crushing = fewer cells broken → less gas
Cold onions = slower enzyme reaction → fewer tears
Fans or running water = gas disperses → eyes survive
chilling onions to 4°C can reduce enzyme activity by ~50% (Block, 2010).
Your Body’s Tear Response 💧
Your tear glands are impressive little machines:
Tear rate: up to 1.2 mL per minute while chopping strong onions (Tsur et al., 1990)
Strong red onions can double this rate
Blinking decreases while chopping by up to 33% because your eyes are focusing on survival
Your tears are literally measurable chemistry in action.
Science-Proven Ways to Beat Onion Tears 🛡️
Chill the onion → slows alliinase by 50%
Use a sharp knife → less cell damage → less gas
Cut near running water or fan → gas disperses
Wear goggles → full chemical armor
Even the pros in professional kitchens use these tricks.
The Moral of the Story: Why Onions Make You Cry
You slice the onion → cells break → sulfur compounds escape
Alliinase enzyme turns them into sulfenic acids
Sulfenic acids turn into syn-propanethial-S-oxide gas
Gas reacts with your eyes → brain signals tears
So no, you’re not weak.
You’re not emotional.
You’re just part of a tiny chemical war happening in your kitchen.
So what do you think? Our Mango is better than Onion 😂
Stay curious, and maybe keep a fan handy next time,
The Mango Fact Team