Listerine has a lot of alcohol in it so beware of causing dry skin!
After finishing my bottle of showsheen I didn't want to put chemicals on my horse so I mixed 6oz of coconut oil and 14oz of apple cider vinegar and topped off the rest of the bottle with water and I'm spraying it on daily. Apple cider vinegar is great at repelling flies and is a good anti fungal by changing the PH, causing fungus to stop growing. It also relieves itching. The coconut oil is good at moisturizing the coat and skin. I also put it in my horse's mane and tail as a conditioner/detangler. Works great so far!
Have you ever used essential oils? Melaleuca (Tea Tree Oil), Peppermint, and Geranium are a wonderful mix with white vinegar and a little water. All ingredients are natural and repel not only flies, but bees and ticks as well. Some people are sensitive to tea tree oil so if you or your horse have sensitivity you can remove from the equation.
Blue Listerine. Cheap and works great
In my natural fly spray I put one part apple cider vinegar (organic unpasteurized), one part water, a LITTLE bit of citronella oil, a few drop of dawn dish soap and however much liquid coconut oil you want (use coconut oil for a show sheen effect)
I love adding Skin So Soft to my mix.
I use 1/3 pinesaw 1/3 water and 1/3 vinger. It works amazing!