Our mastiff had, get this, a yeast-infection in her paw.
She got a yeast-infection in her ear, scratched at it with her paw, it transfered into her pad, and festered there. She subsequently chewed her paw almost to the point of bleeding before we discovered it.
Topical antibiotics cleared it right up, but it was a mystery until we got her to the vet for lab work.
Our vet, at first, said that it could be allergies or just OCD, but it proved to be neither. Get your animal checked out. Only a professional with be able to give you an accurate diagnosis.
I think it's the reason my dog got sick and died. I couldn't get her to stop licking her paws - she licked the fur right off of them, had her to the vet a few times and everything. The vet said it was just one of those things that labs do - shame really :-(
Dogs can lick their paws either due to allergies or also if their paws are sore or causing them grief
I agree, its most likely due to allergies. What food are you using?
If you have checked her paws and have found nothing wrong than the main reason dogs behave this way is due to allergies. Some dogs suffer from something similar to OCD in people and do things out of boredom. Take her to the vet.