"A word of caution about Zoanthids:
I must mention the fact that zoanthids are quite toxic. They produce a substance known as palytoxin (Mebs, 1989) that is one of the most toxic naturally occurring poisons known. This substance was first discovered associated with Palythoa spp. in Hawaii, but has since been found in Zoanthus as well (Fosså and Nilsen, 1998). Palytoxin is apparently produced by bacteria that live in association with zoanthids. A fascinating account about the discovery of palytoxin can be found online on the Wet Web Media site, see reference given.
A strange side note to this is the anecdotal observation I reported in my column Reef Notes in FAMA magazine that this toxin or another one associated with zoanthids may be able to be aerosolized. An aquarist trying to rid his live rocks of a species of Protopalythoa decided to remove the rocks and spray boiling water on them to kill them. A friend of his contacted me after the aquarist was in the hospital and in serious condition, the doctors unable to determine what had caused a serious reaction and respiratory distress. I pointed out the possibility of a palytoxin reaction, but was skeptical about the aerosol or "toxic fumes" that the aquarist believed made him become ill suddenly. The aquarist later recovered, but slowly. In any case, one should be extremely careful when handling zoanthids, Protopalythoa and Palythoa spp., in particular. Rinse your hands thoroughly with soap and water immediately after contacting them. "
from:
http://www.advancedaquarist.com/issues/feb2003/invert.htm
Now the toxin is more stable in seawater then out ....
http://www.cbwinfo.com/Biological/Toxins/Palytoxin.html
But from the same advanced aquarist article above: Protopalythoa spp. have toxic mucus that is able to destroy scleractinian coral tissue, so be careful not to place colonies where they are likely to contact stony corals. I'll discuss this toxic mucus in more detail later in the article.
in sufficient doses this will kill (which is why islanders would use it on their spears to kill other islanders).
Because you don't break out doesn't mean anything - it is like posion ivy - most people have some sort of reaction and a small percentage aren't immediately affected.... the more exposure the more likely you will have a reaction....hell my hands get red and itchy just putting my hands in my tank.....
I'd suggest using cheap rubber gloves whenever handling these critters....