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What is the chemical/s in onions that make your eyes tear? And biologically, why do they tear?
Understanding the Chemistry and Biology Behind Onion Tears
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In summary, onions contain a chemical called syn-propanethial-S-oxide that is released when the onion cells are damaged, causing our eyes to tear up. The best way to prevent tears is to move your head away from the onion or wear goggles while cutting. Alternatively, breathing in deeply can also help alleviate the irritation.
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chroot
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pack_rat2
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From that web-site:
"There are all kinds of remedies for dealing with this irritating phenomenon, some more effective than others. As a general rule, move your head as far away from the onion as you can, so the gas will mostly disperse before it reaches your eyes. If you really can't stand the tears, the simplest solution might be to wear goggles..."
Actually, there's a method I've tried that works very well: breathe in the smell deeply! It causes your eyes to water a lot right away, but after a few seconds, you're no longer bothered.
"There are all kinds of remedies for dealing with this irritating phenomenon, some more effective than others. As a general rule, move your head as far away from the onion as you can, so the gas will mostly disperse before it reaches your eyes. If you really can't stand the tears, the simplest solution might be to wear goggles..."
Actually, there's a method I've tried that works very well: breathe in the smell deeply! It causes your eyes to water a lot right away, but after a few seconds, you're no longer bothered.
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Monique
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Just keep the onion intact while you're cutting it 
FAQ: Understanding the Chemistry and Biology Behind Onion Tears
What causes onions to make you cry?
Onions contain a chemical called syn-propanethial-S-oxide, which is released when the onion is cut. This chemical irritates the eyes and causes tears to form.
Why do some people not cry when cutting onions?
Some people have a genetic variation that makes them less sensitive to the irritant in onions, so they do not experience tearing when cutting them.
Can you prevent crying while cutting onions?
Yes, there are a few methods that can help prevent crying while cutting onions. One is to chill the onion before cutting it, as this slows down the release of the irritant. Another method is to cut the onion under running water, as this helps to wash away the irritant. Wearing goggles or cutting the onion near a fan can also help prevent tears.
Are there any health benefits to crying while cutting onions?
While crying while cutting onions can be uncomfortable, there are actually some potential health benefits. Tears contain natural antibacterial properties, so they can help cleanse the eyes and prevent infection. Additionally, crying can help release stress and tension, leading to a sense of relief.
Do all types of onions make you cry?
Yes, all types of onions contain the chemical that makes you cry. However, some varieties, such as Vidalia onions, contain lower levels of the irritant and may not cause as much tearing when cut.