Michael A. Ball said in
rec.pets.dogs.health:

food, or perhaps environmental ..contact with grass,
chemicals (lawn?), etc

Yes, I'd vote for a contact reaction--to something on the
grass and/or on the carpet.

I'll go against the grain, heh: the only dog I've had who
worried its feet turned out to be allergic to the corn in its
food.

OP: consider that many dogs sublimate medical and behavioural
issues. Paws are often a secondary target.

--
--Matt. Rocky's a Dog.