Advantage II is highly effective when battling troublesome fleas. It targets fleas throughout their entire life cycle and continues to work preventing additional infestations. Advantage will provide your dog immediate relief from biting fleas - literally within minutes - and begins to work against infestations within two hours. It also works as an ideal treatment against chewing lice on your dog as well. A four-month supply is included (apply topically once a month) and is remains effective even after swimming or bathing your dog. For dogs and puppies over seven weeks of age.