Retain a sponge or suitable cloth to leave a trace of oil around the face, belly and other parts of the body where the horse or pony is particularly plagued by flies and midges. Several days of application will result in less insect agitation making the situation more comfortable. FLYBYE Oil is Sitaphal oil the oil from the immature fruit of the custard apple. It has no side effects except that insects do not like it and will consequently tend to be attracted elsewhere. Please note – FLYBYE is not a fly killer and contains no toxic substances that will harm the horse either when licked or through the skin.