FRONTLINE® Plus treats and prevents ticks and fleas on dogs from 2 months old. The two active ingredients, Fipronil and (S)-methoprene combine to work together for the best results. Within a day FRONTLINE® Plus translocates (travels) all over your dog’s body. His/her oil glands slowly and steadily release the product onto the skin where the unwanted pests nestling there will make contact with it. The Fipronil then kills the fleas by attacking their nerve cells.