Science take
(World News Science)

A reaction in the onion releases a chemical factor that irritates eyes. INYT POTENT CHEMICAL IN PLAY Why onions make you cry Onions make us teary because a reaction in the onion releases a chemical called lachrymatory factor, or LF, that irritates our eyes. The onion’s cells break open, allowing two normally separated substances to combine. Linked together like pieces of a puzzle, they become a potent chemical weapon. “It turns into a gas. It hits your eyes, and then it hits your sensory nerves in your eyes and causes them to tear up,” said Josie Silvaroli, an undergraduate at Case Western Reserve University, USA who helped describe how these pieces fit together in a paper...