The main thing that nexgard does is that it prevents convulsions and seizures. Nexgard has recently emerged as a highly effective treatment in the industry. Simparica Bravecto Or Nexgard Which One Is Best Suited For Your Dog American Dog Brown Dog Tick Flea And Tick Afoxolaner, the ingredient in nexgard, works by absorbing rapidly and safely into your pet's bloodstream and causes uncontrolled activity the flea's and tick's central nervous system, which causes death. How well does nexgard work . How long does it take for nexgard to work on mites. How fast does nexgard work? According to the product website, it does not take long for nexgard to start working, as the medication works quickly to kill all fleas and ticks within 24 hours. According to the product website, nexgard works quickly to kill all fleas and ticks within 24 hours. The efficacy of nexgard ® and nexgard spectra ® against sarcoptic mange in dogs was evaluated in a clinical field study. An insec...