You can eliminate the adults, but it is really difficult to get rid of eggs or pupae

Unfortunately for you and your pet, you should be aware that some flea medications, such as pills, collars, shampoo or powders can only kill the adult fleas, but it is quite difficult to get rid of eggs or pupae. So, even if you kill the adults, you can’t get rid of the next generation that is on its way and ready to attack your house. 

According to Dr. Daniel Morris, a professor of dermatology at the University of Pennsylvania School of Veterinary Medicine in Philadelphia, “some products have a compound that keeps eggs from hatching, but don’t kill the pupae.”