One prevalent theory is that the wild frogs live on a diet that includes species of tropical ants that contain the chemicals necessary for the production of their toxin. In captivity, the frogs usually refuse to eat our "northern" ants, whether or not these might contain the necessary chemicals. In any event, the toxin is gradually lost in captivity and captive bred animals are not toxic. Handling the frogs is worse for the frog than for you, so most of us avoid picking them up unless it is necessary, but don't hesitate to dive after an escapee.
So much opinion has changed over just the past few years, that you may still find relatively recent literature warning against touching any of these frogs, but I don't believe any of us have as Maggie points out, experienced any ill effects from handling them.
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Patty
Lost River, Idaho