I don't know how natural this is, but I use Borax powder for fleas. We had a rental house that was infested. The landlord (my BIL) had bombed and there were still fleas. We bombed again (before moving in.) I was at the end of my rope when I used Borax powder (mixed with salt) and sprinkled it all over the carpet. Within 2 weeks, we were flea free (our cats were indoor only and this was before we had our dogs.) I wouldn't put it down if I had a crawling baby, but I think it's ok other than that (and much better than chemicals.) I also put dried mint leaves between the matresses and the sheets and some mint extract on blankets to repel them from the beds.