While chopping onions today, with my eyes burning profusely, someone handed me part of a hot dog bun and said “Here.  Stick this in your mouth.  I don’t know why but it keeps your eyes from burning.”
And it worked.  It was amazing!
WHY does it work, though?!
             
            
              
              
              
            
            
           
          
            
            
              Here, read this.
http://members.aol.com/stevef88/discuss/onions.htm
According to him, it doesn’t work, but it helps. His solution isn’t all that helpful.
This person
http://saramoulton.com/ks_082102.htm
has a better answer regarding eye irritation, but if you still breathe through your nose…
Here’s a more technical answer.
http://www.americanchemistry.com/chemmag.nsf/WebMagazineArticle?ReadForm&mfpk-543ms4
My best solution?? “Honey?? Will you cut up an onion for me?”