Nulli-Fly is a citronella-scented, water-based insecticide formulated for use on horses, with label directions also covering dogs and animal living quarters. The aqueous base resists picking up dust and grime the way oil-based sprays can, and a suspension technology keeps the active ingredients evenly mixed so the bottle does not need to be shaken before use. On horses it can be sprayed directly onto the coat or applied with a sponge or soft cloth after the animal has been brushed to remove loose dirt. The formula is built around permethrin, pyrethrins and piperonyl butoxide, ingredients that work together to knock down and repel a broad range of flying and biting insects. For dog or premise use, the product is sprayed to lightly dampen bedding, resting areas, cracks, crevices and other surfaces where pests may be present. It ships in a single spray bottle and is intended for animal use only, not for use on humans or on cats.