Well, I've handled them for a couple of decades, and did so barehanded for a while, until my fingers began to swell up so hard they felt like rock, and would itch and hurt and stay swollen for days. I now use gloves religiously when moving rock or sand, though not when working with corals.
One thing about marine stings: most are just a nuisance, but I know two completely unrelated lfs owners who didn't wear gloves for many years and now can't even put their hands into a tank to work with corals without reacting, and that's livelihood-threatening. Sensitization takes time. But it may happen to individuals who don't otherwise have troubles with allergies.