do you think the house itself is infested with them or are the dogs getting them from outside bringing them in???
I'd sprinkle the DE around the foundation of the house..
I hate using chemicals on the dogs
But I would bomb the house (as in flea bomb)..Is there a dirt basement?? That might be the problem..or if there are sandy areas outside around..
When I first moved to my house, (14 years ago),,my dogs NEVER had fleas, this house had a high deck that the dogs would go under, all of a sudden I got fleas
I sprayed under the deck and put up lattice to keep the dogs from going under there,,(it was more a dirt/sandy ground) and no more fleas..