If you have horses you have flies. Horses are sprayed daily to keep the pests from biting them and to keep them comfortable. One problem with this is unless you are using a non-toxic, natural flyspray, you are constantly bombarding your horse and yourself with toxic chemicals. This suppresses the immune system, can cause respiratory problems and even cancer. If you read the warning label on the bottle of flyspray many of them will say toxic to the environment, do not contaminate water. Remember these are pesticides that you are spraying on your horse and yourself.
I have seen horses sprayed with flyspray and within minutes go into a seizure and then shake all over for about 15 minutes. I have seen others fall asleep after being sprayed and when brought to the attention of the owner, they simply write it off and say, "oh they always do that". Well, of course they always do that, because they are always being sprayed with pesticides.
There are many natural flysprays that work well and do not contribute to polluting the environment or your horse. One of my favorites is called "Finally Something that Works", or Extreme Shield. Cedarcide provides not only natural flysprays but natural treatments for controlling insects around the stable. These are very effective. Another option is to make your own using essential oils. Think before reaching for the bottle of toxic flyspray.