The invention is a pour-on antiparasitic formulation having superior water resistant properties. The pour-on formulation utilizes one or more polymers (water insoluble with or without water soluble) in the range of about 5 to about 40% w/w, one or more solvents in the range of about 50 to about 94% w/w, with or without additive (e.g., isopropanol or ethanol) in the range of about 5 to about 30% w/w, and optionally a plasticizer in the range of about 0.5 to about 25% w/w. The pour-on antiparasitic formulation features limited spreading when applied to animals (cattle, sheep, dogs and the like). The pour-on antiparasitic formulation further partially evaporates, leaving a water resistant polymer matrix that diffuses at least one active ingredient to the animal's skin.