OMG! I lived on a commune once, and my housemate was having flea issues. I never got bit, only her. So she spreads this diatomacious earth everywhere, floors, doorways, stairs. I refused to let her in my room with the stuff, so she put a huge pile in front of my door. Of course, the whole house was old wood floors filled with cracks, and she was sweeping the white powder for weeks! She never did get it all out of the cracks. Then to add insult to injury, she had picked the wrong kind of powder, and it didn't do a thing!
She was a wing nut. Course so was I back then!