Some zoanthids contain the highly toxic substance palytoxin. Palytoxin is one of the most toxic organic substances in the world, but there is an ongoing debate over the concentration of this toxin in these animals.[citation needed] However, even in small quantities, the toxin can be fatal should it be ingested or enter the blood stream. If delivered immediately, vasodilators injected into the ventricle of the heart can act as an antidote.[1]
In order for this toxin to be dangerous to humans, the average aquarist would need to ingest the zoanthid in sufficient quantities, or brush a recent cut over it. Average handling, propagation and aquarium maintenance is unlikely to pose any danger beyond a localized skin reaction.[citation needed] A 2010 study found toxic zoanthids in three Washington D.C. area aquarium stores.[7]
Palytoxin is a tumor promoter, and is being studied in relation to signaling pathways in skin cancer genesis.[8] Contrary to common belief, palytoxin can be absorbed through intact skin.[9] The danger of acute poisoning from venomous zoanthids is quite real. An aquarist was poisoned through skin injuries on fingers by a Parazoanthus species, but recovered after 3 days. His zoanthid was found to contain 2-3 milligram of palytoxin per gram.[10] For comparison, the intravenous LD50 dose of palytoxin for a grown man is less than 8 microgram. Thus each gram of the offending zoanthid contained enough venom to kill at least 125 grown men.