Why do onions make us cry?

As we know while cooking an onion a very strong aroma is produced that most people enjoy. But cutting up an onion stings your eyes and makes them water uncontrollably. If you love to include onions in your dishes, this probably frustrates you all the time. So just what is it in onions that make them such an ordeal to prepare? When you slice through an onion, you break open a number of onion cells. Some of these cells have enzymes inside them and when they are sliced open, the enzymes escape. The enzymes then decompose some of the other substances that have escaped from sliced cells. Some of these substances quickly rearrange themselves into a volatile gas. The gas reaches your eyes and reacts with the water that keeps them moist. This change produces a mild sulfuric acid, which irritates the eyes. The nerve endings in your eyes are very sensitive and so they pick up on this irritation which is why our eyes sting when we slice onions. The brain reacts by telling your...