No, an interior treatment is not necessary. Exterior treatments will always be the most effective solution for fixing any insect issue. All the insects that are in your home come in from the outside. Almost all insects need to breed, lay their eggs, and feed outside in nature. This means they are going to be moving in and out of the structure multiple times throughout the warmer months. By only applying a treatment on the exterior all the insects that are moving in and out of the home will come in contact with our product and die. We also use a product that will stay effective for up to 2 months so the home will continue killing any insects that land on the home during that time.