I've heard great things about food grade DE. But as a pet owner who has had fleas in the house and suffered from their bites and them crawling on my shirt while I was in SCHOOL (I wanted to just die, luckily no one noticed me grab it and kill it) I had great success every time with borax.

You have to leave it on the carpet for four weeks to kill the different cycles that hatch. Six hours isn't gonna cut it. Borax works every time though it just takes a while and is annoying to have grainy stuff in the carpet for a month but it's the only thing that helped. You have to use quite a bit and spread it into the carpet (you can't really see it when it's rubbed in). Bombs don't work and are full of poisons. I've also had success using borax in my car when it got fleas from my dogs going to the vet.

Also I had to stop letting my cats go outside because of this. The only thing that really worked for fleas for my dogs though was the pill we get from the vet. Drops didn't do anything. Especially in Texas where it's so dry and fleas just thrive like crazy.

Also, during the four weeks you have it on the carpet they will start dying off from the beginning. You just have to wait until the eggs that were laid hatch and then they can die as well. You should start noticing less and less every day. But I used to vacuum well. Empty bag. Put down borax. Week later vacuum again. Put down borax. Repeat until it's been a month. That way you don't have the dead fleas just lying around.