Why Does Cutting an Onion Make You Cry?

Description:  This phenomenon can be used to illustrate both chemical reactions and the particle nature of matter. Onions gather sulfur from the ground to form large organic compounds. When the cells in an onion are breached (during cutting or eating) they release sulfenic acid which becomes a sulfur containing gas that eventually reaches your eye. Your eyes produce tears to remove the irritant. Students could speculate on how the irritant reaches your eyes and even investigate possible solutions to this problem. This phenomenon was submitted by Brian Babulic.

Web Resource:  Science News for Kids - Informational Text Article

This week Reactions takes science into the kitchen. We're looking at the chemistry behind why onion chopping makes you cry. We get to the bottom of this teary phenomenon and reveal exactly what chemical mechanisms trigger it. The video also features a few chemistry-backed tips you can try at home to stop the tears before they start.