There are several methods that can help prevent onions from burning the eyes, including using a fan to blow the fumes away from the face. It is advised when cutting an onion that the cut side always be turned away from the face.
Wearing eye protection like glasses can aid in shielding the eyes from tearing up when cutting onions. Eyewear helps prevent the gases from reaching the eyes.
Wiping the knife with fresh lemon juice can help prevent eyes from burning. Lemon juice also helps lessen the odor from the onion.
To eliminate the risk of stinging eyes, the onion can be placed in a food processor to be diced.