Hi and welcome to YT.
Dawn dish washing detergent will kill any fleas on the dogs at the time of their bath. But, it sounds as though you will also need to treat them with flea meds, either topicals like Frontline, Revolution or with pills like Comfortis. Ask your vet what is working best for your area. You will also need to clean all bedding, carpets, vacuum repeatedly, tossing any vacuum bags immediately in the outside garbage. Flea infestations can be difficult to control but with some hard work and medications you can be successful. Hopefully with cold weather the dogs will have some relief, but the larvae in carpets, etc. can be dormant for some time, so you'll still need to treat and clean.
__________________  ~Ruby, Reno, Razz, & Jack~ |