The most common reasons for biting, licking and hairloss in cats is parasite hypersensitivity (flea allergy, or microscopic skin mites such as Cheyletiella), food allergy, and pollen/dust allergies. Ringworm or fungal skin infection can also cause patchy hairloss and scaling. I recommend that all cats and dogs in the household be treated monthly for fleas with a prescription product such as Frontline, Advantage or Revolution. In cats that are flea allergic, only one bite can trigger a reaction and fleas may not be evident on the coat. If the symptoms persist despite stringent flea control, then talk to your veterinarian about a prescription hypoallergenic diet trial for possible food allergy; unfortunately there is no accurate skin or blood test for food allergy, the test and treatment are the hypoallergenic diet trial for 8 weeks with no other treats or foods. Finally, if the itch persists despite the diet change, consider talking to your veterinarian about referral to a veterinary dermatologist for intradermal allergy testing and desensitization therapy for pollen/dust allergies.
The weight loss is a big concern, and may be related to the stress of the new puppy, intestinal parasites, or to internal disease such as intestinal, liver or kidney disease, or feline leukemia. I am glad that you have an appointment with your veterinarian, they may suggest starting with bloodwork to check her organs/leukemia status, and a fecal exam for parasites. Until the exam, you can certainly try feeding her in a separate room away from the new puppy, or tempting her with smelly canned food.
Kimberly Coyner, DVM
Diplomate American College of Veterinary Dermatology
I'm sorry but we did take her to the vet the December after we got her. When we adopted her she weighed 4 pounds if that (at 10 months old) so we did do periodic vet visits to make sure she was getting healthy. She has since then put on a healthy amount of weight and was where she should be. She's very small for her age. She also had a bad problem with her legs. They were weak and she fell a lot. Exercise and playing with our other cat has made them stronger but DH noticed she's limping and getting clumsy again. She was a stray and is strictly indoor. She had a flea problem but we treated her and she is now cured but still bites and licks herself a lot (and has been, even before we got the puppy). Our other cat doesn't bite himself at all and we make sure our dogs get their monthly flea medicine every single month. The medicine she got when we first got her was for kennel cough (oral for the sneezing, eye for her runny eyes and nose for her runny nose). I'm sorry I keep posting but these are things I also need to remember to tell the vet when we go on Friday.
The vet visit info is approximate. We took her within the first week we adopted her, which I think was July/August of 2008 (it may have been later). She hasn't had any problems except the skittishness. The weight loss and fur has just been recently. When we first got her her legs seemed really weak and she fell a lot but they are a lot stronger so we haven't had to worry about her much.