I found a product at the pet store from a company called Natural Chemistry , product was called Yard & Kennel flea & tick spray. The ingredients were completely natural - cinnamon oil, vanilla, clove oil and cedar oil. I know cedar can be bad for chickens but I sprayed this in an outside area that has been seriously infested with flies and kept the chickens away for a day. The flies are totally gone. The area smelled really nice at first, and I detected a hint of cedar, but after a few hours it mellowed to the point where I didn't notice it. Anyone else use try this product?