Captive bred dart frogs are not dangerous to touch but even though much of their toxin input comes from food in the wild and captive bred animals don't have that, you should always wash your hands after having handled any frog. Dart frogs are a strictly "look, don't touch" frog though - they do not tolerate any handling. If you want a frog you can handle occasionally, get a tree frog. Just be aware that frogs in general are not a handling pet.