NexGard and Frontline are popular flea and tick preventative medications for dogs, but which one is better may depend on your specific needs and preferences. Nexgard flea treatment for dogs is an oral medication taken once a month, while Frontline is a topical medication applied to the skin once a month. NexGard is effective against fleas and ticks, including the black-legged tick, which can transmit Lyme disease. Frontline is also effective against fleas and ticks, but it is not as effective against the black-legged tick as NexGard.