Repel-X PE is an emulsifiable insecticide concentrate designed to be diluted with water before use on horses. The water-based formula combines prallethrin and piperonyl butoxide to repel and kill horn, house, stable, horse and deer flies, along with gnats, mosquitoes and ticks, including deer ticks. Depending on the pests present, the concentrate is mixed at a one-to-seven or one-to-four ratio with water in a sprayer or mixing container. The finished solution is applied with a pressure sprayer or sponge until the horse's coat is thoroughly wet, taking care to avoid the eyes and mucous membranes. A single bottle of concentrate yields multiple gallons of finished spray, making it suited to barns treating several animals. Reapplication is needed every few days for general fly and mosquito control, or more frequently where ticks and biting flies are a persistent problem. The product is not intended for foals under 12 weeks of age.