Tisserand’s definition of the “sphere of action” of a planet is based on the equality of tidal vs. gravitational acceleration ratios of the sun and planet. Öpik and others based their relation on equating the differential solar and planetary forces on a particle. Neither expression was formulated to describe the zone of influence surrounding a planet when considering the small, but significant, long-term perturbative effects of the planets on a particle’s orbital elements. For the purpose of determining these effects on interplanetary dust we derive a zone of influence based on equating the gravitational forces of the sun and planet.