Biting fleas are more than just a nuisance for your dog. Left unchecked, they can cause serious disorders such as flea allergy dermatitis, secondary skin infections, tapeworms, and even anemia. This topical flea treatment lets you stop fleas before they become a problem. Used just once a month, it begins working in minutes, killing 98 to 100 percent of the fleas on dogs within 12 hours and 99 percent of flea larvae and eggs within 20 minutes. The dead fleas can't lay eggs, and the dead larvae and eggs can't hatch, breaking the flea's life cycle and halting the infestation in its tracks. Any new fleas your dog then encounters are killed within two hours, preventing re-infestation for as long as four weeks. In fact, Advantage II is so effective at breaking the flea's life cycle there's no need to treat your dog's environment. Applied before the start of flea season, it helps keep your dog from becoming infested in the first place. Used year-round, it prevents fleas from over-wintering in your home to feast on your dog next season. Gentle enough for puppies as young as seven weeks, Advantage II is water-resistant and continues to work while your dog swims or is bathed. The package includes four pre-measured doses for dogs 21-55 pounds in easy-to-use applicator tubes. For safety, keep out of the reach of children, and read all warnings and instructions carefully.