Why do people get tears when cutting onions?

Question

why?

Answer 1

onions give of mild irritan fumes, thy irritate your eyes, which are very sensitive. im not sure how it works, but i think the moisture in your eye, bonds to the gas the onion gives off, creating a mild acid, your eye compensates for this by crying. i think tears are slightly alkaline, neutralising the acid.

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Answer 2

your eyes are sensitive to the chemicals that are emitted from the onion.  Not all onions emit these chemicals, as least not as strong.  For instance, a vidalia onion normally doesn't cause your eyes to water.  Some white and yellow onions do.  

Answer 3

People have all sorts of interesting and funny ways to avoid this. I had a cousin that used to stick a slice of bread in her mouth while she sliced onions. It was a funny sight watching a grown woman with a piece of bread sticking out of her mouth like a diving board! Usually with tears rolling down her cheeks, too!

Another person I knew used to actually wear a scuba face mask when peeling onions. Guess I know some strange folks...LOL.

The way I avoid it is to start slicing the onion from the STEM side. There is an area about 1/4 inch from the root (hairy) end that has a collection of cells that react to the air and your eyeballs that make them water up. If you don't cut into that area, you probably won't tear up.

Answer 4

Not every onion makes you get tears.

People get tears from cutting onions because the odor of an onion can get so intense, that it will burn your eyes and your eyes will fill with tears.

It helps to run water nearby so it reduces the effect.

Answer 5

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.