Well, first, I have to say that it is very common for many people to feel burning and watering eyes when cut onions. So you do not need to worry about it. And according to some experts, there are kinds of objects in onions which have the irritant function. So when you cut them, it will irritate your tear system and make you just like cry. And also, it will just make your eyes feel burning. To get rid of it, there are many ways you can just have a try. For example, you can breathe through mouth while cutting onions and the mouth is open. And that can be effective. Also, to treat your burning eyes, after you have cut onions, you can just use some ice under your eyes, and it will work for it.