The biggest issue with fleas is you need to treat the area where the dog lives as well. On the odd occasion we've had fleas, it's a major battle. We bathe the dogs with flea shampoo multiple times several days apart. But also, all the carpets, dog bedding, our bedding, furniture, etc. need to be treated as well. Otherwise the eggs just continue to hatch and you still have fleas. It can be a nightmare. Remember to treat your vacuum cleaner as well. The eggs will also live there. For us it usually means a 2-3 week adventure.