i touch my anemones all the time with my hands, and all that happens is the tenticles just stick to my skin.
but once, something fell behind my rockwork, behind my anemones, my magnificas mind you, and the tenticles brushed up against the soft fleshy part on the top of my elbow and i reached behind them.
ouch. quite the sting i got. multiple stings. i had terribly itchy welts on my skin there for the next month, with an annoying bee sting like pain for the next several hours.