The Seresto 8-month flea and tick collar for large dogs provides continuous 8-month flea and tick protection. Unlike oral flea and tick prevention products that require fleas and ticks to bite your pet to work, Seresto flea and tick collar for large dogs kills fleas and ticks through contact, no biting required. Seresto flea collar for dogs is water resistant and remains effective after swimming, shampooing, or exposure to rain or sunlight. (Dogs must not be bathed more than once per month. For dogs that swim once a month or more, the control duration is reduced to five months for flea control, and reduced to seven months for tick control.) Starts to repel and kill fleas within 24 hours of initial application.