We use it with the greys when they are new to the kennel.
That way when new greys come in and if they have fleas they don't pass them along to everyone else.

If you do use it don't be surprised if the dog starts to scratch for a bit of time after you give it to them. The fleas will get a bit active before they die and the dogs may scratch.

Works really well but not for a preventitive normally for quick fix to get the fleas off the dog while your freeing your home from the fleas or if they just came out of the vets office and picked up a flea or two.

Does work really well though