?why do onions make you cry
When you slice through an onion, you break open a number of onion cells. Some of these cells have enzymes inside them, and when they are sliced open, these enzymes escape. Amino acid is one of the substances that escape, and it forms itself into a volatile gas. This gas reaches your eyes and reacts with the water that keeps them moist. This changes the chemical's form again, producing, among other things, a mild sulphuric acid, which irritates the eyes. The nerve endings in your eyes are very sensitive and so they pick up on this irritation. This is the reason why our sting when we slice onion. The brain reacts by telling your tear ducts to produce more water, to dilute the irritating acid so the eyes are protected. Your first reaction is probably to rub your eyes, but this will actually make the irritation a lot worse, of course, if you have onion juice all over your hands.
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i hope you now know why do we cry when we cut the onion