I was helping my mom in the kitchen today, and when I started chopping onions, my eyes started stinging and tearing up. But then I realized something weird – when we eat onions in our food, they don’t make us cry at all!Can someone explain why onions make us cry when we cut them
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The tears are caused by a chemical that is produced by the onion’s defence mechanism. When an onion is cut, enzymes are released from ruptured cells which catalyze chemical reactions which eventually forms a compound called *syn-Propanethial S-oxide*, which is a lachrymator (tear agent). This liquid readily evaporates into gas and the vapors irritate the tear glands in your eyss and cause you to tear up.
Contrary to popular belief this has nothing to do with sulfuric acid, so any answers that purport this myth can be mostly disregarded.
If the onion is cooked, the high temperature *denatures* the enzymes and inactivates them, so you’re not going to have the conditions required to form that tear gas anymore. And any of that S-oxide from cut onions would have evaporated or boiled off in the cooking process, leaving your cooked onions free of the tear agent.
If you’re consuming the onion raw, then having it in your mouth physically prevents some of the tear agent vapors from reaching your eyes once it’s in your mouth, but of course the act of *biting* the onion is basically cutting them and will cause the tear agent to be formed. From inside your mouth, some of the tear agent can still make it to your eyes through your sinuses, so you will probably still tear up, but it might not be as bad as cutting would. This kinda depends on the exact situation.
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