Poinsettias Are Poisonous
"The belief that poinsettia plants are dangerously toxic if eaten, especially by children or pets."
Traces to a single 1919 incident in Hawaii, where a two-year old child died and poinsettia leaves were blamed without any real medical investigation at the time. The claim was then repeated as fact in a 1944 book, Poisonous Plants of Hawaii. When a Cornell University floriculture professor actually looked into the original case in 1972, he found no real connection between the plant and the child's death at all. There's never been a documented poinsettia death since, and toxicology estimates suggest a 50-pound child would need to eat over 500 poinsettia leaves before reaching a genuinely toxic dose.
Myth vs. FactThe entire myth traces back to one unverified 1919 case that, on later investigation, had no real evidence behind it at all.
Sources: Harry L. Arnold, Poisonous Plants of Hawaii (1944); Cornell University investigation (1972); Poisindex Information Service.