It's always easier and cheaper to prevent a flea problem than try to treat them once they've taken over your house. Fleas can get into your carpets, upholstery, wall voids, floorboards, attics, basements, and more. You don't even have to have a pet to be vulnerable to flea infestations. However, there are a number of preventative measures you can take to keep fleas from entering your home, or to keep them from reentering hear home after you've cleared them out.
Check around your house for rodent nests. Destroy any you find. Even as their empty, fleas can be hiding in them.
Ensure that the outside of your house is in good repair. Make sure they foundation, windows and doors, foundation sills, and vents are tightly sealed.
Rodent proof your home; rats are often carriers of fleas.
Fleas are busiest in the summer. You may consider keeping your pets outdoors during this time. Frequent baths and clean bedding will help keep your pet comfortable.
Fleas like organic material; over watering or drying your yard may help keep them at bay, especially in the summer.