Kills 100% of Fleas and Ticks within 24 to 48 hours. Contains Fipronil, a special ingredient that spreads by way of your pet's body oils to nullify a parasite's nervous system, causing paralysis and death. Frontline Plus® also contains methoprene, an Insect Growth Regulator, which makes it impossible for an insect to grow or reproduce. Kills Fleas before they have the chance to lay eggs - thus breaking the Flea life cycle. Generally kills Fleas before they bite, thus reducing the risk of sickness, allergies and disease transmission. Water Resistant - Continues to kill Fleas after swimming, shampooing, rain or exposure to sunlight. In pre-measured, child proof, easy-to-use applicator tubes.