Why do onions make you cry
Anyone who has ever been involved with cutting and peeling onions will know that it can be hard on your eyes as you suddenly find your eyes burning and tears beginning to stream down. Although this is a common phenomenon known to most, the exact reason may not be so commonly known. What actually happens is that on cutting the onion bulb, you release the amino acid sulfoxides from the sulfenic acids which are found inside the onion cells. The product that forms after the released enzymes get a chance to react with the sulfenic acids is known as propanethiol S-oxide and it is this compound which is responsible for making our eyes burn. The unstable compound is in a gaseous form and naturally it rises up towards our eyes. The gas itself would not irritate our eyes enough to make us cry but the trouble begins as the propanethiol S-oxide chemically reacts with the water in our eyes to form sulfuric acid. After the formation of the acid it is only natural that we feel the burn in our eyes and automatically tears are released to wash away the chemicals causing the irritation. The strong smell of onions is also a result of the formed sulfur chemicals and it often is hard to get rid of the smell from your hands even with soap. You either got to allow it some time to fade away or you could try rubbing your hands on stainless steel, which is proven to be effective in removing strong smells.
Although it is only a temporary discomfort, there are ways to even avoid that from happening. The best way is to cut your onions while keeping them submerged in water, in that way, the propanethiol S-oxide gas cannot reach your eyes because it reacts with the water the onion is submerged in. It has also been found that onions that were stored in refrigerators for some time do not cause our eyes to burn as much. Of course there are other external approaches that work as well, like placing a fan in such a way that it blows the gas away from your eyes or just wearing a protective eye gear.