Advantage II for Cats works within 12 hours to kill fleas and only needs to be applied once per month. The product is formulated to address fleas of all life stages, including eggs, larva, and fully-grown fleas. Its three-way protection lasts up to 30 days even when there is frequent water interference. Its waterproof formula ensures fleas are killed on contact to prevent re-infestation on your hound and on your house.