Did you ever wonder why onions make you cry? Slice an onion and the tears start flowing. Why does this happen? Like all other plants, onions are also made of cells; but the onion cells contain sulfur elements.
When we slice the onions, the cells break and release the sulfur vapors. Sulfur has a bad odor, and when these vapors mix with the moisture of our eyes a chemical reaction takes place which produces molecules such as ethylsufine which make your eyes burn.
The eyes then produce tears to wash and and dilute the chemicals – in other words the tears are a natural reaction of the body so that the offensive chemicals can be washed away.
As long as we keep on slicing the onions, more and more cells will break, which will produce more sulfur vapors, and hence more and more tears!
To prevent the tears, try cutting the onions in a bowl of water. The water helps dissolve the sulfur elements, so that they don’t reach your eyes and this prevents the tears from flowing.