Question

When we cut onions why it is making us cry

Answer 1

The synthase enzyme converts the amino acids sulfoxides of the onioninto sulfenic acid. The unstable sulfenic acid rearranges itself into syn-ropanethial-S-oxide. Syn-propanethial-S-oxide gets into the air and comes in contact with our eyes. The lachrymal glands become irritated and produces the tears!

Answer 2

Heya
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Why do we cry when we chop onions?

Ever cut an onion and started tearing up? Most people do. It turns out when you cut an onion, it releases a gas called, ready for this, Propanethiol S-oxide. When mixed with certain enzymes in the onion, it creates a sulfur gas. These gases then get to your eyes and create a mild acid which irritates the eyes.
Normally, your body would signal you to close your eyes. This, of course, is not a good idea if you are cutting an onion. The next best thing your eyes can do is to make tears to protect the eyes. Rubbing your eyes is a bad idea, since your hands are likely full of the tear making onion juice. So how do you keep from tearing up? There are many theories out there. I’ve heard some have had luck burning a candle near the chopping site. (Don’t try that without an adult.) Wearing safety goggles, however, should reduce the tears every time.

NOW YOU KNOW!

hope it helps