Why Do Some Onions Make You Cry More Than Others?
Onions produce a gas called syn-propanethial-S-oxide when cut, which stimulates the eyes’ lachrymal glands, causing them to release tears. The level of this gas varies in different types of onions. Older onions also produce more of this gas, which is why they tend to make people cry more than fresh onions. Additionally, slicing an onion creates more of this gas than dicing or chopping it, which means that the method of preparation can affect how much you cry.