crying Why does chopping an onion make you cry? http://www.loc.gov/rr/scitech/mysteries/onion.html Lachrymatory-factor synthase, syn-propanethial-S-oxide http://www.loc.gov/rr/scitech/mysteries/onion.html http://www.loc.gov/rr/scitech/mysteries/onion.html Everyday Mysteries http://www.loc.gov/rr/scitech/mysteries/onion.html Lachrymatory-factor synthase, Lachrymatory-factor synthase, Library of Congress Why does chopping an onion make you cry? syn-propanethial-S-oxide Lachrymatory-factor synthase, syn-propanethial-S-oxide Why does chopping an onion make you cry? Why does chopping an onion make you cry? chemical irritant http://www.loc.gov/rr/scitech/mysteries/onion.html http://www.loc.gov/rr/scitech/mysteries/onion.html http://www.loc.gov/rr/scitech/mysteries/onion.html Why does chopping an onion make you cry? Everyday Mysteries syn-propanethial-S-oxide everydaymysteries