Biting leg

Does anyone else's staffy literally stick their leg in their mouths and bite them, as if he wants to take it off?

Is this normal, or could it indicate a problem, or even Zeus's way of scratching an itch?

Rocky does this but only for a second or so, I think he doesn't realise how big his own leg is  
Does Zeus chew it or just a little itch? If there are no sores, redness, or signs of anything I would just keep an eye on him to make sure he doesn't make a habit of it If he does seem irritated maybe wipe him down with a damp towel, or have it looked at by the vet if you suspect anything

Check his paws underneath and between his toes, Darcy suffers with allergies and chews her paws sometimes sounds like they're itchy.

Moo nibbles her feet but she just gets into a habit of things so I have to be extra vigilant and stop her, it was the inside of her leg and she made it really sore, broke that habit and then she moves onto something else  

Yeah sometimes when its sore and sometimes when there is nothing there too!