Elanco Seresto Small Dog under 18lbs flea collars will have a performance you expect from topicals, in a collar! The Seresto Flea and Tick Collar provides 8 months of prevention and treatment against fleas and ticks for dogs and puppies 7 weeks of age and older. Contains 4.5% flumethrin and 10% imidacloprid. The Seresto Collar's unique polymer matrix ensures that active ingredients are released slowly and continuously in low concentrations. Collar should be worn continuously; no need to remove for bathing or swimming. Seresto collar kills fleas on dogs within 24 hours and prevents tick infestations within 48 hours. Seresto collar prevents re-infesting and repels ticks as quickly as 6 hours. Seresto collar kills chewing lice for 1 month. Seresto collar aids in the treatment and control of Sarcoptic mange.