Seresto for Large Dogs 8 Month Flea and Tick Prevention CollarSeresto Flea & Tick Collar for Large Dogs over 18 pounds provides continuous 8 month flea and tick protection. This Vet recommended Seresto collar repels fleas and ticks and kills through contact; no biting required. Seresto dog flea collars are made with a long lasting 8 month formula for continuous release coverage over your dog? s skin and coat. They are water resistant* and remain effective after shampooing swimming or exposure to rain or