Advantage For Dogs Over 55 lbs 4 Pack is a once a month topical flea treatment for dogs and puppies 7 weeks or older. Advantage stops fleas from biting in 3-5 minutes and kills 98-100% of the fleas on dogs within 12 hours of application. Advantage For Dogs 100 4pk kills re-infesting fleas within 2 hours and lasts up to 1 month. Kills fleas before they lay eggs. One treatment prevents further infestation for at least 4 weeks. Keeps on working after swimming or bathing.