FRONTLINE Plus has 2 tough killing ingredients. The 1st, fipronil, kills adult fleas and ticks. The 2nd, (S)-methoprene, attacks flea eggs and larvae. It is a topical treatment and work together to kill fleas & ticks all month long. Plus it breaks the flea life cycle by destroying the next generation of flea eggs and larvae. Frontline Plus also give you the power to help prevent flea infestation on your pet. Provides waterproof effectiveness for 30 days.