Not Treating Often Enough Fleas go through a life cycle of egg, larvae, pupae, and adult. Most flea treatments just kill adult fleas, but fleas can continue to emerge for months after you think an infestation has ended. As soon as you finish rinsing the soap, more fleas will jump right back on (and more will hatch).Click to see full answer. Moreover, how long does it take for fleas to die after treatment?Adult fleas will be killed within a few days but the floor should not be vacuumed, swept or washed for at least two weeks after treatment because there will still be eggs which will continue to hatch.One may also ask, what kills fleas on dogs instantly? Give Your Pet a Bath. Just lukewarm water, or water and a mild soap, can help get fleas off your pet’s fur and skin. Comb Your Pet’s Hair Using a Fine-Tooth Flea Comb. Kill the Fleas. Do Regular Checks. Let Your Pet Groom Itself. why is my dog still scratching after flea treatment? The trouble is that other, “new” fleas will replace them. And all the time, the skin can be in a heightened state of sensitivity to the flea bites which keep on happening. Eventually the flea population will decline. Then the skin will settle down and the itching will stop.What do you do if flea medicine doesn’t work? Make sure to apply topical medications correctly (do not split medications to use on more than one pet) Make sure your pet’s skin is healthy so topical flea medications work well. Treat your yard and house where 95-99% of the flea population lives. Kill all fleas as soon as they hatch from the cocoon stage (pupal).