Why is our cat chewing her tail raw?

Our older cat Buddha seems to have become fixated in biting her tail to the point where she's chewing the hair off the end of it.  I'm wondering what we can do for her?  Why is she doing this anyway? She's never done anything like this before.  She is a very skiddish cat.  I know that things upset her like change or new people being around her.  She doesn't even socialize with our other cat preferring to be alone.  

But I am concerned about this new behavior of gnawing on her tail and wonder what we can do to help her stop doing it?

[Jennifer Mathis, D.V.M.]

Please see your veterinarian.  The skin can only respond to problems in a limited number of ways and cats can react to those issues as well.  Having an exam and simple hair/skin tests will likely reveal the problem to your veterinarian and thus to you to get your cat treated well.  Fleas, mites, allergies, other parasites, bladder problems, skin infections can all be factors in what is happening in your cat and how to treat it.  It is highly likely that one or more of these problems is the culprit that needs prompt veterinary treatment.  Your cat is obviously bothered by the situation and your veterinarian can get your cat some relief.

[Kimberly Coyner, D.V.M., DACVD]

I agree with Dr. Amthis, veterinary evaluation is needed. Behavioral causes of self mutilation are possible, but are diagnosed by eliminating other treatable medical causes such as parasites, bladder pain, spinal pain, etc.