Well this is just a guess really as I’m really sure but I think there is a certain chemical released form the onion cells when you cut into them and this then irritates your tear ducts which makes them water. Thats why it varies between onions (different amounts of the chemical) and people (different sensitvities to the chemical).
Well my mommy says that since she has been wearing contact lenses that she doesn’t cry when she peels onions, so I guess they must help.
I am the biggest baby when it comes to peeling onions, if I walk into a room where someone else has peeled an onions, i’ll often have to leave because my eyes are streaming so much…so I must be really sensitive!
One great trick I have learned though is that if you peel the onions underwater it helps a lot but the one that works for me is chewing gum! I have no idea how it works though.
I think I can add a little something here.
Apparently when you cut an onion things mix which are apart in a whole onion “sulfenic acids” mix with “enzymes” this produces something new…..”propanethiol S-oxide” this is the bit that makes you cry! This is volatile which means it drifts up and gets in your eyes in your eyes it reacts with your tears to form “sulfuric acid”!!! Sulfuric acid burns your eyes and that makes make you make more tears so you cry!
Ways to prevent it involve stopping the gas getting to your eyes, so either using googles or having a fan blow over the onion or to slow down the reaction and this can be done by cooling the onion before cutting (put it in the fridge) or cutting underwater.