NexGard is a tasty chewable tablet for dogs which kills fleas and ticks by over-stimulating their nervous system. The active ingredient in NexGard is afoxolaner. The afoxolaner is absorbed into the bloodstream after taking the chewable tablet. Fleas and ticks attach to your dog and begin to feed. As a result, they are exposed to the active ingredient and the effect occurs within 8 hours (fleas) to 48 hours (ticks). The effect against fleas will last 5 weeks, and the effect against ticks lasts 4 weeks. Because NexGard is an oral product, swimming or bathing has no effect on NexGard.