The way you should use diatomaceous earth for fleas depends on whether or not the flea problem is inside your home, outside your home, or on your pets. If you have fleas on your pets, chances are good that you also have fleas inside or outside of your home depending on where your pet stays most of the time. You should be able to safely apply the diatomaceous earth directly onto your pet's skin and brush it into the carpets of your home or sprinkle it around your baseboards if you don't have carpet. Cutting down on the flea population around the outside of your home might also be possible by sprinkling diatomaceous earth around your yard, concentrating on areas where fleas are the worst.
If you are using diatomaceous earth for fleas on your pet, be sure to massage it into your pet's skin as thoroughly as possible. It might be a good idea to use more diatomaceous earth on the areas of your pet's body where fleas tend to congregate, such as the nape of the neck and stomach. Fleas often attempt to hide on pets in areas where pets cannot reach to scratch themselves. Diatomaceous earth is generally considered safe to use on animals, but it is important to keep it out of the eye area because it could cause some irritation there.
Using diatomaceous earth for fleas in your home varies slightly depending on whether you have carpet. If you have carpet, you can use a carpet brush and work the diatomaceous earth into the carpet. After four or five days, you should be able to vacuum the diatomaceous earth up along with several dead fleas. In homes with hardwood floors or linoleum, fleas tend to congregate along the baseboards and in corners. You can use the diatomaceous earth for fleas in these areas if you don't have carpet and leave it in place for several days before sweeping or vacuuming it up.
Diatomaceous earth also tends to be helpful for killing fleas outdoors, although the chances of killing all the fleas in your yard with this method are slim. If you sprinkle diatomaceous earth around the perimeter of the outside of your home, concentrating on the areas where fleas tend to be the worst, you should be able to eliminate at least a portion of the flea population. This might be incredibly helpful if your pets live outdoors and are continually having problems with recurrent flea infestations.