grooming her hair off

Question
I have a 10 year old female cat that has 'groomed' her side, and base of her tail until her fur is Very short.  I've massaged vitamin E oil into spots she makes raw, it seems to help heal.  She's never alone very long. I say that because she was abandoned but I've had her for 4 months and this has just started.  I don't know what to do.

I've tried;

Sponge bath & foam bath- she likes it
added fish oil to her food,once a week or it's hard on her system
upgraded her food

Answer
Cats eat their hair off (Barbering) as a way to scratch itching.  Usually this is caused by allergies.  Your vet can give a long acting shot of a steroid and that should help relieve the itching so she will stop this behavior and allow the hairs to regrow.