When chopping onions we break open a number of onion cells. These cells all contain enzymes which then very quickly decompose some of the other substances which have been released from the cells. Acids are then created which very quickly combine and transform themselves into a gas. The gas travels to the eye and then reacts with moisture in the eye, creating a very mild form of sulphuric acid which makes us cry. In other words, our eyes ar ehaving a chemical reaction to sulphuric acid.
There are remedies which can be used to minimise the release of enzymes and so reduce the acid created. One of these is to chop the onion under a tap or in a bowl of water. This sound seasy, but is quite difficult to do in practice. Another suggestion is that peeling the onion and then chilling it before chopping gives more time before the acid is released. But there is no single remedy which is 100% effective !
There are remedies which can be used to minimise the release of enzymes and so reduce the acid created. One of these is to chop the onion under a tap or in a bowl of water. This sound seasy, but is quite difficult to do in practice. Another suggestion is that peeling the onion and then chilling it before chopping gives more time before the acid is released. But there is no single remedy which is 100% effective !