Fly sprays for horses – chemical, fatty acid, or essential oils?


Fly season is coming up, which means we must declare war on flies right now. A trip to the feed store or tack shop will quickly get your head spinning about what fly spray to use… so here are the basic types of fly sprays.


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Chemical fly sprays for horses are designed to knock down and possibly kill flies.


  • Sometimes the chemicals that knock a fly down are strong enough to kill it, and sometimes not. Many larger flies of the horsefly family, like greenheads, are too large to be affected by the fly sprays out there.


  • You will commonly find pyrethrin as an ingredient in horse fly sprays. Derived from chrysanthemums, pyrethrins need to come into contact with a fly.


  • The pyrethrin then enters the bug’s nervous system to knock it off your horse. Often they are paired with synergists to keep the pyrethrins circulating in the bugs long enough to kill the bugs.


  • You will also find permethrin, another neurotoxic agent, in fly sprays. These chemicals are similar to pyrethrins but last a bit longer to kill the flies.


fly spray bottle with ingredients


Both permethrin and pyrethrins are broken down by sun and oxygen, so there’s little toxic risk to the environment, but other animals are at risk.


  • This also begs the question of how long they last on your horse….oh wait, just found the answer…. pyrethrins last an hour or two, maybe longer, depending on the other ingredients in the spray.


  • Pyrethrin is toxic to fish, bees, and birds, while permethrin is toxic to bees, cats, and fish.


  • Pyrethrins and pyrethroids, such as permethrin are downright toxic to cats and will kill them. Treatment is possible, but the entire process is heartbreaking and expensive. Do not even touch your barn cat if you have sprayed your horse or touched your horse after using fly sprays with these chemicals.


Fatty acids in fly sprays


  • These often funny-smelly sprays are designed to mask your horse’s location from flies that rely on a chemical trail to find your horse.


  • The fatty acids mimic your horse’s natural (and weak) bug-repelling smells to create a cloud of confusion around your horse.


  • Your horse is unbothered, and the flies MIGHT get to live. This type of fly spray won’t work against the flies that rely on a heat signature or sight to find a meal.


ecovet fly spray on horse's legs



You can also find fly sprays that are largely based on essential oils.


  • Lavender, peppermint, and lemongrass are popular essential oils for fly sprays.


  • The evidence for fly repelling abilities of these fly sprays are based on antidotes, not science, so it’s hard to say if they work or not, and if so, what flies they work on.


  • Many recipes also include vinegar, which for some bugs, like the many species of gnats out there, is actually an attractant. Some insects and flies use smell to locate their next landing spot, and essential oils definitely put off a smell.



  • You might be doing some research with your local agriculture extension service to find out about the flies in your specific area. Then you can create a plan and experiment with fly-repelling strategies.





For fly-busting products, you can pick up these to add to your arsenal. As an Amazon Associate, I earn from qualifying purchases, which are at no additional cost to you. I greatly appreciate your support! You can also visit my Amazon storefront here:  PEG storefront.

Fly Whisk

For *mostly* bug free riding

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Farnam Equi-Spot, Horse Fly and Tick Control, 12-Week Supply for One Horse

This spot-on product kills and repels ticks and helps with mosquito control.

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Cashel Quiet Ride Horse Fly Mask with Long Nose and Ears
$32.99 $29.99

This style is great for riding!

06/24/2024 05:13 pm GMT
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Summit Mosquito Dunks
$9.84 ($4.92 / Count)
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Rub Protector Lycra Fly Mask – GG Equine

These fly masks are fantastic for protecting ears and eyes, and do great under halters and grazing muzzles to stop rubs and hairless patches.

Use code 15PROEQUINE for a sitewide discount on muzzles, halters, accessories, and slow feeders.

Thanks guys!