FRONTLINE Plus for Cats doesn’t just kill adult fleas and ticks but also slays the next generation of flea eggs and larvae. Plus, it works non-stop for 30 days on cats. FRONTLINE Plus for Cats has 2 tough killing ingredients. The 1st, fipronil, kills adult fleas and ticks. The 2nd, (S)-methoprene, attacks flea eggs and larvae. They work together to kill all month long. Plus, it breaks the flea life cycle. By destroying the next generation of flea eggs and larvae, Frontline Plus gives you the power to help prevent new flea infestation on your pet. Frontline products are highly recommended by veterinarians for flea and tick control for cats.