These very small small fleas prefer a dog as a host but will also feed on cats, humans and wild animals. Within 2-4 weeks an egg is fully developed into an adult flea. Dog Flea’s can transmit tapeworms that infect animals and humans. When fleas bite humans, they can develop an itchiness of small bumps that will possibly bleed. This rash can generally be found around elbows, knees, or ankles. When dogs are bothered with fleas, they scratch and bite themselves, particularly in areas around their head, neck, and tail. Flea infestations can not only be aggravating for both dogs, cats and humans, but also very dangerous. They prefer to live in bedding, carpet, and fur .