Homemade Horsefly Repellent - 6 for horses / 1 for human Repellent #3 Get the ingredients―1 cup vinegar and baby oil, 1 tablespoon dish soap and Skin so Soft, 1 cup water, and ¼ cup Pine-Sol. Take all the ingredients and mix it in a bowl. Then pour in a spray bottle. Shake the bottle properly before you spray it on the horses. The spray will keep flies and gnats away, plus keep the coat shiny.