Ask A Scientist© Biology Archive

name        Marquita
status      student
age         16

Question -  Why does onion make the eye watery?
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Dear Marquita:

http://www.pa.msu.edu/sci_theatre/ask_st/021297.html
http://www.uselessknowledge.com/explain/onion.shtml

Sincerely,

Anthony R. Brach, Ph.D., brach@oeb.harvard.edu
http://www.herbaria.harvard.edu/~brach/
Flora of China http://flora.harvard.edu/china/
Harvard University Herbaria, 22 Divinity Avenue, Cambridge, MA 02138-2094 USA
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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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