K9 Advantix II Large Dog 30-day treatment & prevention protects dogs 21-55 lbs. from fleas, ticks, mosquitoes, biting flies and lice Kills fleas within 12 hours of application Vet-recommended formula kills & repels on contact so fleas don’t have to bite your dog to die Easy-to-apply topical treatment is fragrance-free and waterproof after 24 hours No prescription needed