Dd is 18 months old. When she gets frustrated (e.g. a toy wont do what she wants it to, or I have taken something away from her, or she is asking for something and I cant understand what she means) she grabs whatever is near her and bites down hard on it. This is often a toy or a book but it has been my arm or finger (she drew blood once). She hasn't done it to anyone else and she is at a childminder full time during the week.
Is this normal? How should I react when she does it?