Something seems wrong

Question
We have 3 cats...all heathly beautiful babies.  Samantha, the mum of the other two loves to have her back scratched, yet, today something seems wrong.  When we scratch her towards the lower part of her spine, before where her tail starts, she 'buries' her head so to speak and starts biting anything in front of her.  At first we thought may be it was the cushion she was sitting on {may be she didn't like it}, but it doesn't seem to matter where she is.  No purring, nothing, just and instaneous urge to bite 'things' directly in front of her.  As I'm writing, am wondering now if this could be a neurological situation, but what?  Very concerned!!  Do you have any ideas?   Respectfully ~

Answer
It sounds like she's itchy down there to me.  Usually when a cat makes a scratching or biting motion when touched in a particular area, it signals that the area is very itchy or uncomfortable.  Maybe she was bitten by a bug of some sort in that area.  Maybe she's allergic to something in her food or the environment.  Maybe she's picked up mites (scabies) or fleas somehow.  Maybe she's having some auto immune disease.  Or she may have an itchy bacterial infection, like staph, or funal infection, like ringworm.  Those will usually cause some flaky or scaley skin, however.  

Cats can develop a rather rare disorder called feline hyperesthesia, or Rolling Skin Syndrome.  It causes extreme discomfort along the back and tail.  In most cases, the cat has episodes that come and go.  Cats may bite when petted in that area, chew at the area (sometimes until it bleeds), run throughout the house trying to escape the pain...some zone out and may even hallucinate.  It's believed to be related to a seizure disorder in many cases, and some cats are greatly helped by taking a seizure medication.

It doesn't sound like a life-threatening situation to me.  But because it arose so suddenly, it does sound like something that should probably be investigated, especially since some of the diseases I mentioned can spread to the other kitties and to you.