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. 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 a is water-resistant flea medication, so it continues to kill fleas even after a shampooing, swimming, rain or exposure to sunlight. Advantage® is for Dogs over 7 weeks and Cats over 8 weeks old. Do not use Dog product on Cats or Cat product on Dogs.