Izzy bit my hands and arms, drawing blood, relentlessly to the point that I would get very depressed and wonder if buying her was a mistake. We tried yelping, removal, standing with our backs turned, arms crossed and ignoring. The vet said 'puppies bite' and suggested chews, bones etc. Eventually she grew out of it and never bites us now. I can't remember at what age it stopped, probably 5 months ish.