Seresto Flea & Tick Dog CollarsSeresto Flea and Tick Collar for Dogs Kills fleas within 24 hours and ticks within 48 hours after initial application. Re infesting fleas are killed within two hours and reinfesting ticks on dogs are killed in as quickly as six hours. As the active ingredients wear off the dog. The flea and tick collar replenishes the hair and skin with a new supply of active ingredients, providing continuous protection against fleas and ticks for eight months. Repels