we use 5% sevin dust on about everything from the pets to the gardens.
We can spray under our house and for that we use malathion and have never had a problem using either,Malathion will take care of the fleas and will also take care of an ant problem by spraying next to the house all the way around.
We quit using flea shampoo on our pets and now was the outside in a tub using dawn dishwashing detergent and the fleas literally drop off of them.
Have never used the DE and am hesitant about using it. I just figure if it will cut up worms inside my chickens what is it doing to their stomachs? Have not read up on it enough yet to be comfortable using it but just had my own opinion that it would be about like me eating something with finely ground glass in it. Will have to study up on it more and then I may try it.