A simple homemade horse fly spray can be made with just apple cider vinegar, water, and a small amount of dish soap, though adding essential oils like citronella or peppermint will boost its repelling power. These DIY sprays won’t last as long as commercial products containing synthetic chemicals, but they’re a practical, affordable option when you’re willing to reapply throughout the day.
The Basic Three-Ingredient Recipe
The simplest version requires only three ingredients you likely already have: apple cider vinegar, water, and dish soap. Mix 2 cups of apple cider vinegar with 1 cup of water and add a squirt or two of dish soap. The soap acts as a surfactant, helping the vinegar-water mixture cling to your horse’s coat instead of running off immediately. Pour it into a spray bottle, shake well before each use, and you have a functional fly deterrent.
This base recipe works on its own, but it’s more of a mild deterrent than a strong repellent. For better results, especially during peak fly season, you’ll want to add essential oils.
Essential Oils That Repel Flies
Essential oils work through what’s called spatial repellency. As they evaporate off the horse’s coat, they create something like an invisible bubble of scent around the animal that flies avoid crossing. The oils most commonly used in horse fly sprays include:
- Citronella, one of the most widely recognized insect repellents
- Peppermint or cornmint (also called wild mint)
- Lemongrass, closely related to citronella
- Clove oil, which has a strong scent flies dislike
- Rosemary
- Thyme
- Geraniol, a compound found naturally in geraniums and roses
- Cedarwood
To upgrade the basic vinegar recipe, add 10 to 20 drops total of your chosen essential oils to the 3-cup batch. Using two or three different oils tends to work better than relying on just one, since different fly species respond to different scents. A popular combination is citronella, peppermint, and lemongrass.
Essential Oil Safety for Horses
Never apply undiluted essential oils directly to your horse’s skin. Essential oils are highly concentrated plant extracts, and without proper dilution they can cause irritation, redness, or allergic reactions. Always mix them into your vinegar-water base or a carrier oil before spraying.
Some essential oils are specifically unsafe for horses. Avoid blue tansy, garlic, yarrow, clover bud, wintergreen, and birch essential oils entirely. Tea tree oil and eucalyptus are toxic if ingested, which makes them risky choices for a spray your horse might lick. While both appear in some commercial products at carefully controlled concentrations, they’re better left out of a DIY mix where precise formulation is harder to guarantee.
Before spraying a new recipe all over your horse, do a patch test. Apply a small amount to the soft skin near the elbow on the upper front leg, then leave it alone for 24 hours. Check the area the next day for swelling, redness, hair loss, flaky skin, or heat. If the skin looks the same as the surrounding area, the spray is likely safe for full application.
How Long Homemade Sprays Last
This is the biggest trade-off with going the DIY route. Natural repellents break down faster than synthetic ones because sunlight and oxygen degrade the active ingredients. A commercial spray containing permethrin or pyrethrins can offer protection for several hours or more. Homemade sprays with essential oils and vinegar typically need reapplication every one to two hours, sometimes more often.
Sweat, rain, and humidity speed up the breakdown even further. On a hot day when your horse is sweating during a ride, you may need to reapply as soon as you notice flies returning. Natural fly sprays also don’t kill insects. They only deter flies from landing, which means the protection fades the moment the scent dissipates.
If your horse is turned out all day, a homemade spray alone probably won’t cut it. Pairing it with physical barriers like fly masks, fly sheets, and fans in the barn gives more complete protection.
Tips for Better Results
Store your homemade spray in a cool, dark place when not in use. Since UV light breaks down the essential oils, a clear spray bottle sitting in the sun will lose potency quickly. An opaque or dark-colored bottle helps.
Shake the bottle thoroughly before every application. Oil and vinegar separate naturally, so without mixing you’ll get uneven concentrations, some sprays heavy on oil and others that are mostly water. Focus your application on areas where flies tend to congregate: the belly, chest, legs, and around the ears and face. For the face, spray onto a cloth first and wipe it on rather than spraying directly, which can startle the horse and get product in the eyes.
Some horse owners also add a tablespoon of mineral oil or a light carrier oil like coconut oil to the mix. The oil slows evaporation slightly, which can help the spray last a bit longer on the coat. It also adds a slight sheen that some flies find harder to land on. Just be aware that oil-heavy formulas can attract dust and make the coat look greasy if overused.
When Homemade Spray Makes Sense
DIY fly sprays work best for horses with skin sensitivities that react to commercial products, for owners looking to reduce chemical exposure, or as a cost-effective daily option when you’re around to reapply regularly. A batch costs pennies compared to commercial sprays, and you can adjust the recipe based on what your horse tolerates and what seems most effective against your local fly population.
For situations where you need long-lasting, heavy-duty protection, like turnout during peak horsefly season or trail rides through marshy areas, commercial options with synthetic repellents still outperform homemade versions. Many owners use both: a natural spray for daily grooming and barn time, and a stronger commercial product for high-exposure situations.