Flea shampoos are certainly safe and will not harm your beloved pet. Whether they are effective or not, however, is another matter.
A flea shampoo is only successful at killing adult fleas that are on your pet’s body, but will do nothing about the next generation of fleas that are readying themselves for attack.
Fleas usually lay eggs directly on the body and fur of its host, in this case your pet. When the animal moves about, the flea eggs are often brushed off and deposited in different areas of your home, especially the location where the animal sleeps and rests.
These eggs will hatch more fleas to simply replace the ones that were killed by the flea shampoo. In order to successfully eliminate a flea infestation, you must disrupt the fleas life cycle.
The best way to do this is by using a modern flea medication such as Advantage, which will prevent the adult fleas from breeding and laying more eggs. This will ensure that in a short period of time the flea infestation will be eliminated.
I consider flea shampoos more of a temporary solution to a flea problem rather than a viable long-term solution.