new guy here with a cat question

back in high school a friend of mine had an overweight cat that whenever you would pet him at the base of the tail, where it meets the body, he would clean his front legs constantly until I stopped petting him there. Well, a few months ago we took in a stray with the same issue, only it's worse. this one is a neutered male and his sensitive area starts half way down his back. if he is touched near the base of his tail, he wips his head around (almost violently) to clean the area. sometimes he will clean his legs and other times he will try and scratch or bite, but he never runs away which leads me to think it's not painful. is this a problem or is it just a feline characteristic of some cats? thanks for any help.

They have a lot of nerves there and it feels so good to them that sometimes the reaction is a nip or crazy grooming. My cat likes the air and makes weird chewing noises.

I would think his skin itches there. Maybe from being dry?

I think it is just a "cat-thing".
Our Toby has always started licking his front paws when we pet his belly....almost like it feels so good he does`nt know what to do with himself.
Tedy has never done this till recently....I think he`s seen Toby do it so now he is imitating him. (Toby also taught Tedy to "talk" ,as Tedy was completely silent whe we first got him....now he`s almost as much a "gabber" as Toby is....plus Tedy can now even imitate Toby`s voice and sometimes I can`t tell who`s talking unless I see them!)
Linda

yep, it is what I call the cleaning button. Blueberry does it. When you scratch at the base of her tail she will immediatley start grooming herself. Stop, and she stops. It is pretty funny. Little kids I have shown this to think it is really a button. Just a way to have fun with it