–Answered by Ryan Elkins

The tearing of the eyes is a result of enzymes that form a sulpherous gas when the onion is cut (concentrated inside the inner core or bulb of the onion) being released into the surrounding air.

You have a few options to avoid this - one would be to not cut through the center of the onion but to extract the “core”. This is kind of a pain and means you are discarding a decent chunk of onion, so I don’t like it too much.

Another option is to use a fan to blow the gases away from you. A small fan next to you blowing horizontally should do the trick.

You could also wear goggles, although you’d have to leave them on for a while until the gas dissipates from the area.

Another technique is to cut a lemon in half and rub the fresh lemon against both sides of the blade. You’ll have to keep “refreshing” the juice coat and your onions will have some lemon juice on them, so this is somewhat limited by that factor.