The advent of such products as Advantage and Frontline has revolutionized flea control. There is no excuse for any dog having fleas. These products can be used on puppies as young as 6 weeks. If you want to save money, buy a package for a 50 to 100 LB dog and apply the liquid as directed with a 3 cc syringe. Get correct dosages and syringes from your vet. If you are in an area with ticks be sure to get products that kill ticks too. Some even kill mosquitoes that are the vectors of heartworm.