I am a chihuahua breeder and have been for 30+ years. I use Frontline Plus. It is safe on pups 8 weeks old. If you just use soap on your pup that will not stop the fleas. Fleas spend most of their lives off your pet and in your carpets multiplying. When your pet bites a flea, it can get tapeworm. Fleas are nasty. Also, don't apply Frontline for 2 days after bathing your pet. Frontline works by moving through the oils in your dog's hair. Don't bathe your pet until 2 days after applying it also because it will not be spread through the hair enough and you will be removing it before it works. www.YankleeBelleChihuahuas.com