Accepted Answer

The most common reason that a cat is going to constantly mow at their fur in this specific area is flea infestation. Your veterinarian should thoroughly evaluate your cat for the presence of fleas, and the kitty should be on a monthly safe and effective flea preventative such as Advantage, Frontline, or Revolution. Even if you do not see any fleas on your cat, if she is allergic to the flea saliva, then just one flea on her can drive her absolutely crazy. For this reason, all cats and dogs in the house should be on an effective montly preventative product. In some cases, cats can cause themselves a secondary bacterial infection in their skin (pyoderma) which needs to be treated with oral antibiotics for several weeks.
Although you did technically treat her for fleas, the products that you used are not very effective. Flea collars simply do not work, and powders can be helpful on small kittens but not really on adult cats. So, I would not rule fleas out completely until a more effective product like one of the ones that I mentioned above is used.

Other common causes of this behavior in cats are feline scabies and cheyletiella. Scabies and cheyletiella are both mite infections that can be diagnosed with a test at the veterinarian called a skin scraping. This is treated with oral or injected ivermectin given over the course of several weeks.

In some cases, cats do this activity as an anxiety or compulsive disorder. This usually responds to treatment with serotonin reuptake inhibitors such as fluoxetene and paroxetine. In some cases tricyclic antidepressants such as amitriptyline are efficacious.

I am attaching some client information handouts that I use in my practice that discuss these conditions in more detail. I hope that you find them useful.

Click Here
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I hope that this information is of help to you, and that your kitty feels better soon. Please let me know if I can be of further assistance.

Dr. K.

Expert:	Dr. K
Pos. Feedback:	99.5 %
Accepts:	1123
Answered:	5/13/2009

Veterinarian

9 years experience as Veterinarian