A recent residential case had us researching this!  We did not write it, but found it informative…

Five Reasons Ghosts Bite

ATTENTION – a Ghosts of any age sometimes bite to get attention. When real ghosts are in situations where they are not receiving enough positive attention and daily interaction, they often find a way to make others sit up and take notice. Being ignored is not fun. Biting is a quick way to become the center of attention – even if it is negative attention.

IMITATION – Many ghosts do love to imitate others. Watching others and trying to let them know they are around they show their presence to a haunted location. Sometimes as we all do ghosts see others bite and decide to try it out themselves to see if they can affect the living.

TERRITORY – Some believe that real ghosts are trying so hard to show possession of a location. “Mine” and “Me do it” are words that come to mind. Learning to do things independently, making choices, and needing control over a situation are part of a haunting. Biting is a powerful way to control others. If you think about it, it is a quick way to get what you want.

FRUSTRATION – You have to realize that a ghost as being what it is experience a lot of frustration. Being Dead is a real struggle. Consider this when they can’t find a way to make people hear their words to express their feelings, they resort to hitting, pushing, or biting.

STRESS – A real ghost’s world can be stressful, too. A lack of daily routine, interesting things to do, or interaction with loved ones or just another human being are stressful situations for the dead. When a person transits to the other side they also experience stressful events of what they see family members going through. Biting is one way to express feelings and relieve tension. It is also a way to show persons that you do not like what they are doing.

Website source: http://www.hauntedamericatours.com/ghosts/BitingGhosts.php
Author: By Lisa Lee Harp Waugh