I can not think of any harm in trying. I know that fleas do not weigh enough to disturb the surface tension of regular water. This means they float on top, don't drown, and can jump off. If they are put in soapy water then they sink and drown. Bathing your dog in liquid soap will definitely kill (drown) and wash away SOME of the fleas, but there is no guarantee that even if you bathed the dog a hundred times that you would get them all. Even if you killed ALL of the fleas, the moment you put your pet back into your fleas infested house or yard, more could jump on. I read somewhere that only about half the fleas in a house are actually on your pet(s) at any given time. Soap doesn't repel fleas or kill the fleas that bite your pet. I've heard that only Dawn Liquid Soap works. (I've never bothered testing others though.) Either way you should probably bathe the dog in a gentle conditioner after a soap bath. The soap is a harsh irritant that is made only for use on humans' hands and arms. It was never meant to come in contact with more sensitive tissues or with non-human skin. Make sure you rinse thoroughly since pets groom themselves with their mouths and left-over suds could upset their stomach or hurt their skin. A soap bath can help reduce the number of fleas in your house and on your pet and it will lessen the pet's torment but soap baths are not adequate replacements for real, vet-approved flea remedies. Baker or brewer's yeast and garlic are two natural flea repellents for dogs. (Garlic is BAD for cats.) You can buy tablets or powders at pet stores to slip inside treats or sprinkle on food and water. The garlic is formulated so that it is odorless and won't make your pet smell. There are also odorless garlic tablets for you, so that the fleas will leave you alone. Neither kills fleas, though. From experience, I can tell you that garlic and yeast work better at preventing your pet from becoming infested than at repelling starving flea hordes off of you and your pets. This means get chemicals, natural or otherwise, to kill the fleas, then give your dogs garlic and yeast to keep the fleas from coming back. There is still no guarantee, however.
Yes it does work. I speak from experience. I've raised MANY orphaned kittens and often times they were given to me with PLENTY of fleas on them, but not old enough for dips or flea shampoos. Wash the pet in Dawn. It HAS to be DAWN as no other liquid dish soap is the same. Keep lathering for at least five minutes and rince completely. Wrap pet up in warm towel and keep wrapped or covered until they are completely dry- especially for very young and small animals.Treat your carpets or grassy areas so the pet will not become reinfected once you let them back down to walk around again.
It only kills the fleas short term and possibly not all of them so they will be infested again shortly. I suggest to go to the vet and get Frontline put on, it works wonderful and it kills the fleas and prevents further infestation.