Fleas depend on a blood meal from a host to survive, so most fleas are introduced into the home via pets or other mammal hosts. On some occasions, fleas may become an inside problem when the host they previously fed on is no longer around. Then fleas focus their feeding activity on other hosts that reside inside the home. An example of such a situation is when a mouse inside the home is trapped and removed, the fleas that previously fed on the mouse are then forced to feed on pets or people.
Employing exclusion practices is important for many pest problems, but exclusion does not have a major, direct benefit for flea control. However, sealing cracks, gaps and holes to help keep rodents or other potential hosts from gaining access into the home is an important indirect way to keep fleas outside. The most effective ways to keep fleas from getting inside the home is to eliminate outdoor flea habitats and outdoor hosts, plus using area-wide flea control chemical products and veterinarian-approved flea control products on pets.