Dave,

Two of my cats love, I mean *love* to lick plastic (plastic bags, wrappers,
anything).  I have asked the vet about it and she says it's probably just
that they like the way it feels on their tongue.  Sometimes licking can
indicate a mineral deficiency.  If your cat is compulsively licking herself
(more than just the usual grooming), or there are "raw places" on her then
she needs to see a vet - could be an allergy or infection.

Meghan

 Hi Dave ,
Poor thing that must be sore !
My cat licked a bald patch on her tummy becuase she is flea allergic
and also because of the pain from cystitis.  I've also put her on a
diet that doesn't have additives. Some cat foods you can buy are also
wheat free.

http://www.marvistavet.com/html/body_food_allergies.html

http://www.marvistavet.com/html/body_inhalant_allergies.html

http://www.marvistavet.com/html/body_eosinophilic_granuloma.html

Sometimes  licking starts due to itchyness but becomes a compulsive
habit so even if the cause is dealt with the cat carries on  licking.
Cats also over-groom to relieve stress caused by boredom or
frustration .
   Alison