i don't really know about the washing (i know if there's a bed bug problem, you can either wash the clothes and hang them out in the sun, or you can plastic bag them and put them in the freezer. fortunately i have not had to try this out but people say it works) but i was just reading that article that's on here somewhere that says the reason we don't have fleas in our homes in colorado (they exist mostly on wild animals but once they jump to cats or dogs, they perish) is because it's so dry.
if you can buy a humidifier, i wonder if there's anything opposite that would dry the air out. that's probably impossible when the air outside is humid, but i don't know anything about safe flea treatments or even natural ones from my own experience.
Incredibly enough, such devices exist! They're even called... wait for it...
"DE-humidifiers" :wink
(Apologies for the touch of snark, your comment just made me laugh! :wink
Seems like it would be not a terrible addition to more standard treatments, if you've got a particularly humid house. Depending on where you're living, might also make the summer heat more bearable without turning on the air conditioner. I should note that if you do have an "air conditioner", it will act as a dehumidifier anyway.
I would also note that for pests, freezing's often less than ideal... What works better seems to be a black garbage bag left in full sun; starves them (speeds up their metabolism, and without a food or water source...) instead of preserving them (cold tends to slow metabolism, so they can survive
longer without food or water). I'm not sure how long fleas specifically would survive in the freezer, but in general heat treatment's more effective than cold treatment.