Crying and Onions
Why does onion make the eye watery?
Anthony R. Brach, Ph.D., firstname.lastname@example.org
Flora of China http://flora.harvard.edu/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
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.
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Update: June 2012