Abstract: A pet door fluid/powder applicator device disposed upon the bottom of the flap of a typical pet door. The pet door fluid/powder applicator device includes at least one roller volubly disposed on an underside of a chamber. At least one interior cavity is disposed within the chamber. The cavity is configured to store fluid/powder in contact with a first portion of the roller. The fluid/powder is applied to the hide of an animal as the animal is caused to contact and rotate the at least one roller of the rollers. Thus, whenever the animal moves through the pet door, a dosage of the fluid/powder containing a desired active ingredient is applied to the animal.