Chives are in the genus Allium - look here
http://www.aspca.org/site/PageServer?pagename= pro_apcc_toxic_onion
And this:
The use of garlic and other members of the Lily family such as onions, shallots, and chives in the cat's diet is not advised. Ingestion of these plants in a raw, cooked, or dried form can lead to damage of the red blood cells, which are rejected by the body from the bloodstream, and a continued use of garlic or onions can eventually result in hemolytic anemia. If the anemia is not controlled by discontinuing the use of the plants, it can potentially lead to death. Less significant but important is that raw garlic and onions irritate the mouth, esophagus, and stomach and can cause or exacerbate ulcers.
"An alkaloid, N-propyl disulphide, present in both cultivated and wild onions, chives, and garlic, affects the enzyme, glucose-6-phosphate dehydrogenase, in red blood cells that interferes with the hexose monophosphate pathway. Oxidation of hemoglobin results because there is either insufficient phosphate dehydrogenase or glutathione to protect the red blood cells from oxidative injury. The resulting formation of Heinz bodies within erythrocytes is characteristic of onion poisoning. (...)"
Marielle Gomez-Kaifer, PhD, Department of Chemistry, University of Miami