Previously published on The Optical Vision Site
According to the National Onion Association sulphuric compounds are released into the air from a cut onion, irritating the eye and causing it to tear. Their advice to reduce tearing: first chill the onions for 30 minutes and then cut off the top and peel the outer layers leaving the root end intact. (The root end has the highest concentration of sulphuric compounds that make your eyes tear.) There you have it…a way to fewer tears the next time you cut a thick slice of onion for that grilled cheeseburger.