Advantage II for dogs is for use only on dogs and puppies 7 weeks of age and older and weighing 11-20lbs. Kills fleas within 12 hours of application. Kills reinfesting fleas within 2 hours. Advantage II uses two active ingredients for flea prevention and treatment. Imidacloprid kills adult fleas on the animal. Advantage II also kills flea larvae, flea eggs and chewing lice. The insect growth regulator pyriproxyfen inhibits development of immature stages, effectively breaking the flea life cycle.