Toxicological Trivia from March 09, 2010: With flowers and leaves of red, green, and white, poinsettias are widely used in holiday decorations. Even though public health officials have reported that poinsettias are safe, many continue to believe this is a poisonous plant.In an analysis of 849 575 plant exposures reported to the American Association of Poison Control Centers,17 none of the 22 793 cases involving poinsettia resulted in considerable poisoning. No one died from exposure to or ingestion of poinsettia, and most (96%) did not even require medical treatment. In 92 of the cases, children ingested substantial quantities of poinsettias, but none needed medical treatment, and toxicologists concluded that poinsettia exposures and ingestions can be treated without referral to a healthcare facility. Several studies have failed to highlight the active principles present in other species of Euphorbia. They are:
a) Toxic diterpenes;
b) Saponins;
c) Oxalate.

Correct answer a: read more in Spanish news; About low toxicity of  Poinsettia and other christmas miths fall. Also in original paper of BMJ