Fallacious yet widespread and documented beliefs courtesy of Wikipedia.
Poinsettias are not highly toxic. While it is true that they are mildly irritating to the skin or stomach and may sometimes cause diarrhea and vomiting if eaten, an American Journal of Emergency Medicine study of 22,793 cases reported to the American Association of Poison Control Centers showed no fatalities, and furthermore that a strong majority of poinsettia exposures are accidental, involve children, and usually do not result in any type of medical treatment.