— Turn on a fan to blow the fumes away from your face.
— Wipe the cutting knife with lemon juice. (Lemon juice will also neutralize the smell of onions on your hands after you finish working with onions.)
— Cut the onion under water.
— Wear goggles.
— Chew gum.
— Hold a piece of bread or a wooden matchstick in your teeth.
— Breathe only through your mouth.
But the U.S. National Onion Association recommends the following: First chill the onions for 30 minutes. Then, using a sharp knife, cut off the top and peel the outer layers leaving the root end intact. (The root end has the highest concentration of the sulphuric compounds that make your eyes tear.)
Source: U.S. National Onion Association