Zodiac Infestop II Flea Topical Solution for Dogs kills fleas rapidly and protects for up to 4 weeks. It controls fleas within 1 day of treatment and may reduce flea allergy dermatitis. Your pet can be shampooed, immersed in water or exposed to rain 3 days after treatment and Infestop II still retains its ovicidal and larvicidal efficacy for up to 4 weeks. This pack contains a 4-month supply.