The most common reason for a cat the 'chew' her fur is itchiness and inflammation of the skin underneath, this is the cats way of scratching an itch. There are many reasons what a cat might be itchy.
The top of my list in cats is always flea allergy dermatitis. Even though you may not see any fleas on her doesn't mean there aren't one or two lurking and oftentimes this is all it takes for a cat with flea allergy dermatitis. These cats are allergic to the flea's saliva so it only takes one flea to bite to set off the allergic response. Once the allergy is under way (i.e. she gets a rash and/or starts chewing her fur) she may require antiinflammatories as well as the flea treament to break the itch-scratch cycle.
It is important to ensure that you are always using a quality flea treatment appropriate for her weight all year round (such as Advantage, Revolution or Frontline) you may also need to flea bomb your home.
In the long-term flea allergies are avoided by strict flea control - every 3 - 4 weeks with Advantage or Advantage Multi or every 7- 8 weeks with Frontline. You must also ensure all dogs and other cats, in the household are treated at the same time. Very sensitive animals may also require periodic long-acting steroid injections.
To rule out a food allergy, you need to undertake a food trial with a 'hydrolysed protein' diet such as Hill's Z/D ultra allergen free and this needs to be fed SOLELY for 3 weeks minimum to see a response. Cats can develop intolerance to a diet they have been fed for a long time, so a diet change is not a necessary precursor. After this time if you are seeing a change in your cats symptoms you can slowly introduce different foods week by week with the guidance of your Veterinarian.
Contact allergies are best treated by avoidance of the plants that are to blame, but identifying the exact cause of a contact allergy can be very hard. A referral to a skin specialist may be the way to go for either a skin patch test or a blood allergen test if this is suspected.
It is also possible (but less likely) that your cat may have skin mites or lice as they commonly cause intense itching and irritation. Usually a Veterinary check up for a skin problem involves physical examination and possibly a skin scrape to check for mites and lice, as well as signs of fleas.
There are a few things you can do in the meantime to help alleviate his itching:
- a medicated shampoo (these often require 10 minutes in-contact time which can be very difficult with cats)
- if only a small area is affected you can apply Neosporin cream sparingly twice per day.
However, it is very important for all skin problems to determine the cause before further treatment is begun.
Hope this helps,