I think it is mostly a puppy thing, Ruby did this at first, but lately seems to have stopped. I always offer her a toy to chew on instead of my fingers. Our trainer suggested "Bitter Apple" spray to put on anything you don't want chewed on . We have tried it and she didn't like it at all, but it was a hassle to spray on my fingers and be sure to wash off before eating anything. Playing with a toy instead of my hands is working best so far.
