Is helium dangerous?

Helium itself is non-toxic, however, if you breathe nothing but helium, you are not getting oxygen. Inhaling a few puffs from a balloon is not dangerous, but continuing to do so without taking breaks to breath air inbetween can be dangerous. People have died from asphyxiation (smothering) by helium, but this could happen with any gas that displaces oxygen from the air you breath.