Ever wondered why does onions make us cry?
So when you cut an onion, its cells are broken up which allows to release Amino acid sulfoxides form sulfenic acids. Sulfuenic acids is a volatile acid which syn-propanethial-S-oxide, which being volatile in nature reaches your eyes, where it meets water to form sulphuric acid. This acid formation in the eyes burns your eyes and release tears to clean them.
So next time when you cry while cutting the onions, you must be knowing the reason - the culprit syn-propanethial-S-oxide.
How can you avoid them?
Keep the onion in refrigerator before cutting it, it will slow down the reaction speed.
A high speed fan, which moves the volatile acid to another direction rather than reaching your eyes.
Lit a candle near, it will absorb the gas formed.