Why Do Onions Make People Cry?

Onions make people cry due to a series of chemical reactions that occur when an onion is cut. When an onion is sliced or chopped, its cells are damaged. Inside these cells, there are enzymes called alliinases and molecules known as sulfoxides. When the cell walls are broken, the alliinases come into contact with the sulfoxides. This interaction leads to the production of a volatile compound called syn - propanethial - S - oxide.

This syn - propanethial - S - oxide is a gas that is released into the air around the cut onion. When this gas reaches our eyes, it reacts with the water in our tears. The reaction forms sulfuric acid, which is an irritant to our eyes. Our eyes are extremely sensitive organs, and when they detect this irritant, they trigger a protective mechanism. The lacrimal glands, which are responsible for producing tears, are stimulated to produce more tears. The increased tear production is an attempt to wash away the irritant and protect the eyes from further damage.

Interestingly, different onions can cause varying levels of "crying" because the amount of sulfur compounds they contain can differ. For example, onions grown in sulfur - rich soil tend to have a higher concentration of these compounds, making them more likely to cause tears. Also, the freshness of the onion matters. Fresher onions usually have a higher concentration of the necessary enzymes and sulfoxides, so they are more likely to trigger the tear - inducing reaction. Some people have also developed various methods to reduce the impact, such as cutting onions under running water or in front of a fan, which helps to disperse the syn - propanethial - S - oxide gas before it reaches the eyes.