Have you ever chopped an onion and found yourself wiping away tears? You’re not alone! Onions have a sneaky way of making our eyes water, but why does this happen? And more important—can we stop it? With a few fun experiments for kids to explore the mystery behind onion tears and test some wacky, science-backed (or just plain silly) tricks to see which ones actually work!
Why do onions make you cry?
Onions contain sulfur compounds that help them grow and protect them from hungry animals. When you cut into an onion, you break open its cells, releasing an enzyme called alliinase. This enzyme reacts with the sulfur compounds in the onion to create syn-propanethial-S-oxide—a gas that irritates your eyes.
Your eyes have a natural defense system: tear production! When the gas reaches your eyes, your body sends tears to wash it away, making you cry.
But what if we could stop the onion from making us cry? People have come up with plenty of creative ways to do just that—let’s test them!
Fun experiments for kids to learn how to stop the tears
Gather some onions, a cutting board, and a few household items, and let’s explore whether these popular tear-stopping tricks actually work! First, you may want to download this guide to cutting onions.
Experiment 1: The wet paper towel trick
🔬 Hypothesis: A wet paper towel placed near the cutting board will absorb the onion gas before it reaches your eyes.
What You Need:
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1 onion
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A knife
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A cutting board
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A wet paper towel
Procedure:
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Wet a paper towel and place it next to your cutting board.
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Start chopping the onion and observe whether your eyes water.
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Repeat the experiment without the paper towel to compare results.
Science Behind It:
The theory is that the gas from the onion is attracted to moisture, so it gets absorbed by the wet towel instead of floating into your eyes.
Experiment 2: The bread-in-your-mouth test
🔬 Hypothesis: Holding a piece of bread in your mouth while cutting onions will absorb the gas before it reaches your eyes.
What You Need:
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1 onion
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A slice of bread
Procedure:
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Take a bite of bread but don’t chew—just hold it in your mouth, letting part of it hang out.
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Start chopping the onion and see if your eyes water.
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Try chopping an onion without the bread and compare your results.
Science Behind It:
The bread is thought to absorb the onion gas before it reaches your nose and eyes.
Experiment 3: Chewing gum while chopping
🔬 Hypothesis: Chewing gum will prevent onion-induced tears.
What You Need:
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1 onion
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A piece of gum
Procedure:
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Pop a piece of gum in your mouth and start chewing.
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Chop the onion and see if your eyes water.
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Compare to chopping without gum.
Science Behind It:
Some believe that chewing forces you to breathe through your mouth, which may draw in the onion gas before it can reach your eyes.
Experiment 4: Holding a spoon in your mouth
🔬 Hypothesis: Holding a metal spoon between your lips while chopping onions will redirect the onion gas away from your eyes.
What You Need:
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1 onion
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A metal spoon
Procedure:
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Place the spoon handle in your mouth (like a dog with a bone!).
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Start chopping and see if your eyes water.
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Compare results with and without the spoon.
Science Behind It:
This trick isn’t exactly backed by science, but some people swear by it!
Experiment 5: Lighting a candle nearby
🔬 Hypothesis: A candle will burn up the onion gas before it reaches your eyes.
What You Need:
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1 onion
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A small candle and matches/lighter
Procedure:
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Light a candle and place it next to your cutting board.
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Chop the onion and observe if your eyes tear up.
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Compare to chopping without the candle.
Science Behind It:
The flame is supposed to burn some of the tear-inducing gas before it gets to your face.
Experiment 6: Rubbing lemon juice on the knife
🔬 Hypothesis: Lemon juice will neutralize the onion enzymes, reducing the amount of tear-inducing gas.
What You Need:
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1 onion
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A knife
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Lemon juice
Procedure:
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Dip a paper towel in lemon juice and rub it on the knife blade.
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Chop the onion and see if your eyes water.
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Compare to chopping without lemon juice.
Science Behind It:
Lemon’s acidity may break down the onion’s enzymes before they release the irritating gas.
Experiment 7: Using a Potato
🔬 Hypothesis: A raw potato will absorb the onion gas, preventing tears.
What You Need:
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1 onion
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A raw potato, cut in half
Procedure:
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Place a cut potato near your cutting board.
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Chop the onion and see if your eyes water.
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Compare with and without the potato.
Science Behind It:
This trick is more of a kitchen legend than proven science, but it’s fun to test!
What fun experiments for kids works best?
After testing these tricks, which one worked best for your family? Some people swear by the wet paper towel trick, while others think chewing gum or holding a spoon in your mouth is the way to go. Experimenting helps kids explore science in a hands-on way, and they get to experience how different methods impact the same problem.
If you want to keep onions from making you cry, try using a combination of these tricks. And if all else fails, just embrace the tears—after all, they’re a sign that onions are packed with natural compounds that make them both flavorful and healthy!
Want to try other fun experiments for kids? Good Housekeeping has compiled 45 of the best science experiments.
To learn more about onions go to our FAQ section here.
Looking for recipes specific to the onion you have? Nature’s Ninja has you covered here.
