Palythoas contain palytoxin, a kind of organic toxin, which is one of the most poisonous organic compounds on Earth. Luckily they only exude small amounts of it, and you would have to consume a small multitude to actually die from it. People who suffer from allergies to cyanoacrylate and other organic compounds should not handle zoanthus, because they are under higher risk of being allergic. This can result in amputation of a limb.