Fleas primarily come from outdoor environments where they live in shaded, humid areas such as tall grass, sand, sheds, debris, and under shrubs. They thrive in warm, moist conditions and are often found in places where animals frequent, like yards and wildlife habitats

. Fleas attach themselves to animal hosts-commonly pets like dogs and cats, as well as wild animals such as raccoons, foxes, squirrels, opossums, skunks, and stray cats. These animals carry fleas into homes, where the fleas can then infest carpets, furniture, pet bedding, and other indoor areas

. Fleas begin their life cycle as eggs laid in these outdoor environments or inside homes. The eggs hatch into larvae and pupae in the environment before adult fleas seek a warm-blooded host to feed on. Because fleas spend much of their life cycle off the host, simply treating pets is often not enough to eliminate an infestation

. In summary, fleas originate outdoors in natural habitats or areas frequented by infested animals and are brought into homes mainly by pets or wildlife. They can also be introduced via contact with infested animals or even on clothing or belongings that have been outside