fleabusters
There's much discussion of flea control here. Does anybody else use / have experience with this company? The product is polyborate salts; much like borax if I've got it right. Dessicates fleas, not a neurotoxin. They basically dust your carpeting and upholstery with the stuff; sort of reverse-vacuuming.
Many years ago (20?) when we had wall-to-wall carpeting and a cat and many fleas, we had them do our house and I thought the efficacy far outlasted their 1-year guarantee. I'd say it's worth a try based on our one experience.
We're in Seattle -- mild temperatures and quite damp except July-September -- it might work better or worse in different climates.
How much carpeting you have may also be a big factor. We don't have much anymore.