The following has been successfully used to repel flies from cows: Nitro benzine, 5 ounces; carbolic acid, 3 ounces; kerosene oil, 3 ounces; sol. formaldehyde, 1 ounce; fish oil, 1 1/2 quarts. Mix and just touch the hair with the mixture. To Destroy Fleas. My barn, is full, of fleas I tried to destroy them by using creso-dip, but did not kill them, all.