why do onions make you cry?!

Best Answer - Chosen by Voters

>There are lacrimaric compounds, mainly sulfur based, in onions that do that. They are related to sulfur based amino acids I believe.

When you cut an onion, you break cells, releasing their contents. Amino acid sulfoxides form sulfenic acids. Enzymes that were kept separate now are free to mix with the sulfenic acids to produce propanethiol S-oxide, a volatile sulfur compound that wafts upward toward your eyes. This gas reacts with the water in your tears to form sulfuric acid. The sulfuric acid burns, stimulating your eyes to release more tears to wash the irritant away.

Cooking the onion inactivates the enzyme, so while the smell of cooked onions may be strong, it doesn't burn your eyes. Aside from wearing safety goggles or running a fan, you can keep from crying by refrigerating your onion before cutting it (slows reactions and changes the chemistry inside the onion) or by cutting the onion under water.

Since you say you have to cut onions fairly often, why don't you buy one of those little table-top fans (like they use in nail salons at each station) and place it on the counter, aiming it directly at the onion you're slicing? This might blow that sulfur compound away so it won't "waft up toward your eyes."

chemistry.about.com

Answer has the best explanation of why onions make you cry when you cut them. Keeping them cold reduces the problem somewhat, but onion goggles make the chore easy. They're goggles with a dense foam lining that keeps the sulfur fumes from reaching your eyes. A friend of mine bought me a pair a couple years ago, and I thought they were a joke and stuck them in a drawer for a year before I finally tried them. Now I use them every time I chop onions. I can mince them fine, and not cry!

http://www.amazon.com/RSVP-International…

As you are cutting they release a very fine mist of hydrochloric acid.

Tip.
Slice with a sharp knife and don't chop.
Chill for up to an hour in the fridge.

tips: let COLD water flow over the onion for a minute before start cutting it and you wont cry

The liquid inside the onion can burn eye
why?
because they are onion