The tree and its parts contain strong toxins, some unidentified. Its milky white sap contains phorbol and other skin irritants, producing strong allergic dermatitis. Standing beneath the tree during rain will cause blistering of the skin from mere contact with this liquid (even a small drop of rain with the milky substance in it will cause the skin to blister). Burning the tree may cause blindness if the smoke reaches the eyes. @Curionic
Even more curious? Check out this great article by Montem Outdoor Gear - Common Hiking Injuries & How To Treat Them - Great article on how to cure those nasty blisters and other common hiking injuries.