Question: Why do onions ,are you cry

Jennifer Paxton answered on 14 Mar 2018:

oh super question!
Onions contain a chemical that is irritating to the eyes and makes them ‘water’ or produce tears. When you chop up an onion the cells of the onion are cut open and this releases the chemical into the air. Now this chemical is very volatile, meaning that it changes from a liquid to a gas very quickly indeed, and so the gas rises up and hits our eyes – that’s when the stinging starts!! When it hits the watery outside of the eye, the gas dissolves into an acid and that starts to irritate the surface of the eye. Because your eye is now irritated (and probably stinging quite a bit!) you start to produce tears from the lacrimal gland in your eye. The lacrimal gland sits just above each eye (slightly towards the outside of your skull) and it produces the liquid you know as tears. It will produce lots to wash away the acid and make your eyes feel normal again. Of course, your eyes will probably look very red for a wee while but this is totally normal they they will look better soon.