Palytoxin's some serious stuff. My little story is pretty benign compared to this poor guy who lost his dog, but I'll share it anyhoo.
I was messing with a colony of zoos several months ago (was a green matting-type colony), and ended up dropping them (polyp-side down) into another rock. They closed up and starting spewing out this milky-gray liquid. Stupid me, didn't think much of it, went plunging right back in and finished my tinkering. I had a cut on my hand at the time which STUNG like a ***** for several hours afterwards. The skin around the cut puffed up and got very red. The discomfort went away which was followed by a mild numbness around the cut which lasted through the next day. I have no way of knowing if the zoos were responsible, but I strongly suspect it.
With the large amount of reefers out there and the small amount of cases of serious poisoning, I tend to think the risk is small. But it's still something to think about. I know I'm a little haphazard when working in my tanks, but after this experience, I wash well after playing in there.