Onions make you cry because they contain a chemical irritant called syn-propanethial-S-oxide. When you cut into an onion, it releases this compound into the air. When the irritant comes into contact with the sensitive surface of your eyes, it triggers a series of reactions as a defense mechanism.
![](https://www.manuscriptedit.com/scholar-hangout/wp-content/uploads/2024/04/Publication-Package-Services-BANNER.jpg)