Advantage Flea Control is a monthly application that kills 98% to 100% of fleas and their larvae within 12 hours. In addition, re-infesting fleas are killed within 2 hours. Kills fleas before they have the chance to lay eggs - thus breaking the flea life cycle. Effective up to 6 weeks! Advantage is applied to the back of the neck on cats and between the shoulder blades on dogs. It spreads naturally on the skin surface at the hair root level, aided by body movement to provide whole body coverage. Advantage is water-resistant flea medication, so it continues to kill fleas even after shampooing, swimming, rain or exposure to sunlight. Advantage is for dogs over 7 weeks old. Do not use dog products on cats or cat products on dogs.