We had fleas a couple months ago and our dog is allergic to the flea bites. The fleas didn't seem to physically bother the cats, but it was driving me crazy. We tried various pet flea shampoos and Frontline. Nothing worked. Ended up getting oral Comfortis for the dog and topical Revolution for the cats. Those meds, along with vacuuming carpets/furniture and washing the dogs bedding every day worked wonders. The Comfortis is expensive, but it's worth it in the long run. The vet also told me that shampooing with a dish soap, like Dawn will help kill the fleas. You coat the dog with Dawn (the dog not being wet yet), first applying the soap in a ring around the top of the neck creating a barrier to the face and then applying to the base of the tail, the genitals, the anus, the feet and between each toe. This prevents the fleas from getting on the face or hiding in those other areas. Then you coat the rest of the fur. Leave the dish soap on for about 10 minutes, this allows the fleas to smother. Add some water and lather up working the soap thru the fur. If you can, comb soap through with a flea comb, cleaning the comb of fur and fleas after each swipe. Rinse the dog thoroughly to get rid of all the soap residue. This won't prevent fleas, but it will kill the fleas on the animal by suffocating them and the dish soap is gentler than the flea shampoos with all the chemical. Good luck. The vacuum will end up being your best friend, lol