Our beautiful girl Cassie (border collie x kelpie) seems to always be licking 1 spot on her back, off to the side of her tail (roughly).
I have had a look and there is nothing there, no cut, no fleas, no difference in skin color etc but i was wondering if there is a reason she is doing it?

You can see a patch on her fur where she licks it, you can see where her saliva has dried.

Is there something i should be looking at or is this normal doggy behavior?

It's actually quite annolying , it's the most dusgusting sound to hear her doing it