How many times have you had to chop an onion only to find tears streaming down your face when you’re done. When onions are cut the enzymes and chemicals react with each other to create a vapor that causes your eyes to tear.
There are a couple ways to cut many without crying. One creates quite a fashion statement while the other needs a little foresight. One way is to simply wear goggles. These can be simply swimming goggles, wood shop protection goggles, or even ski goggles. They are kind of clunky, not very attractive, but they get the job done.
The other way is to simply pop the onion into your refrigerator about an hour before you need to chop it. The lower temperature makes the reaction slower, which means less vapors are released to cause your eyes to tear.
That said, there are all kinds of other old wives tales about how to not cry when cutting an onion. If something works for you by all means feel free to do it. These are just some tried-and-true methods that you might want to try as well.