Hamsters bite humans for many reasons and require special handling to avoid biting. A hamster may bite out of stress, pain or fear, and it may bite because it is untame.
Additionally, hamsters bite when they are disturbed from sleep, while eating or approached too quickly from an unfamiliar angle. Hamster owners should always make their presence known before reaching into the cage and grabbing the hamster, and they should never try to handle a hamster while it is eating or sleeping. A person may also be bitten when breaking up a hamster fight, which should only be done with gloves or a towel rather than bare hands.