Click Here for Application DirectionsClick Here for Warning InstructionsFor the treatment and prevention of fleas and ticks on cats and kittens from 8 weeks of age. FRONTLINE Plus Cat Tick & Flea treatment combines fipronil, the active ingredient in all other FRONTLINE products, with (S)-methoprene, an insect growth regulator. This combination effectively kills fleas on the pet, and breaks the flea life cycle by inhibiting the development of flea eggs and larvae.