Most fly sprays for horses do not work because they are intended to keep insects from biting which means that the entire animal must be covered to prevent this from happening. Obviously, this is a monumental task at best. In scientific terms it means that the repellent is trying to push the insects away.
There is a much more effective way of dealing with biting insects. It is called the masking method.
Ole Time Woodsman Fly Dope has been protecting outdoor enthusiasts and their animals from all biting insects since 1882. Long before DEET and other chemicals were invented. And here is why: All humans and animals emit a flume of carbon dioxide when they breathe. This is what attracts all biting insects to your horse. Ole Time Woodsman formula, even though it is over 130 years old, actually interferes with an insect's ability to detect the carbon dioxide flume. It creates a mask of protection around your horse so that insects cannot find them.
This is explained scientifically in this chart in a study done by:
Anandasankar Ray, Department of Entomology, Center for Disease Vector Research, University of California Riverside, Riverside, CA 92521, USA;
Do not try to "Push" insects away, but rather "Mask" the carbon dioxide flume with Ole Time Woodsman Fly Dope Ranch and Farm Formula.
"I put this on my ponies' forelocks and immediately the Noseeums were gone! It was amazing to see!"
Jessie from Ponies-go-Round