Frontline Spot OnFrontline for Dogs is not only an effective flea treatment it also treats ticks and biting lice and can be used in breeding, pregnant and lactating bitches. Frontline is available in pack sizes of 3 or 6 pipettes and for different sizes dogs.Frontline for Dogs Spot On is applied by snapping the top from the upright pipette and then applying between the parted hair of the shoulder blades on the dog. You should wash your hands after use. Frontline for dogs kills fleas within 24 hours of contact with the active ingredient fipronil and most fleas will be dead within 48 hours. However there are fleas within the environment and eggs that may hatch that can reinfest the dog but Frontline will remain active killing these fleas as they come into contact with the treated dogs. An environmental flea spray for the house should be used in conjuction with this product and because fleas may still be seen does not mean that the Frontline for Dogs is not actively working.