Give your dog long-lasting protection against fleas and ticks with the number-one vet-recommended flea and tick collar*. Unlike other flea and tick protection, Seresto large dog collars kill and repel fleas and ticks for 8 continuous months. Seresto collars make your dog's comfort a priority by killing fleas and ticks through contact, so pests don't have to bite your dog to die. Existing fleas die after 24 hours of initial application of the collar. After 24 hours, any new fleas on the dog are killed within 2 hours with protection against further flea infestation lasting 8 months. The prevention of infestations with new ticks starts at 48 hours after application of the collar. 48 hours after application, any new ticks are repelled and/or killed in as quickly as 6 hours. Seresto large dog collars protect against common pests like deer ticks, American dog ticks, brown dog ticks, and Lone Star ticks; they're also effective against chewing lice for 8 months. Fleas and ticks not only cause discomfort; fleas can transmit bartonellosis or tapeworms. Ticks can transmit Borrelia burgdorferi, which causes Lyme Disease. Check the product label for information on potential side effects. Seresto large dog flea and tick collars are for dogs at least 7 weeks old and over 18 pounds, and no prescription is needed. They're odorless, non-greasy and water-resistant to swimming, exposure to rain or sunlight, bathing, and shampoo treatment.* Seresto is a trademark of Elanco or its affiliates. * Seresto large dog is water resistant and remains effective following a shampoo treatment, swimming or after exposure to rain or sunlight. Under normal conditions, effectiveness lasts for 8 months. In order to maintain an 8-month duration, 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 5 months for flea control and reduced to 7 months for tick control.