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Name: Marquita
Status: Student
Age: 17
Location: N/A
Country: N/A
Date: N/A 

Why does onion make the eye watery?

Dear Marquita:


Anthony R. Brach, Ph.D.,
Flora of China
Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA 02138-2094 USA

Basically, onions have a protein and an enzyme that when mixed together produce flumes that will react with the tear fluid of the eye and the irritation is weak sulfuric acid. These two components of the onion are separated by membranes until the onion is cut open. Actually, if you cut the onion under water, the tearing will not happen.

Steve Sample

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