Understanding Water-Based vs. Oil-Based Equine Fly Sprays

There are two different foundational approaches to fly spray: oil-based products and water-based products. Oil-based fly sprays are usually made with ingredients that come from oil called petroleum distillates. These oil ingredients may create other problems.

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We’ve all been there—staring at the fly spray options on the feed store shelf. What is the difference? While there are many different active ingredients, there are two different foundational approaches to fly spray: oil-based products and water-based products.   

Oil-based fly sprays are usually made with ingredients that come from oil called petroleum distillates. The idea behind these products is that the repellant ingredients will not evaporate as quickly with an oil foundation. However, these oil ingredients may create other problems like:  

  • Burning. Much like a tanning oil, they can amplify the sun’s rays.  
  • Drying. They may make your horse’s coat shiny when applied, but can dry out the skin even resulting in cracking.  
  • Residue. They leave a sticky and even smelly residue behind  

Water-based fly sprays are easier on most horse’s skin and won’t attract dirt or dust. Though easier on your horse’s skin, you’ll want to make sure your water-based sprays include synergists in the formula to keep them from breaking down in environmental conditions (sunlight, rain, sweat, etc.). 

So, what can you do to make sure you pick the best fly spray for your horse?

  • Read the small print. The product claims in the big print are the manufacturers’ sales pitch, or what they think will convince customers to buy that product. While this language is highly regulated by the EPA, it’s the small print—the list of active ingredients and their percentages—that tells you the most. Since the types and levels of active ingredients vary from one fly spray to the next, knowing more about the formula of the fly spray you’re considering will help in determining how well it will work.
  • Know the active ingredients in your horse’s fly spray and what they do. Active ingredients include insecticides, repellents and synergists. Insecticides are what kill the insects, repellents prevent insects from touching your horse, and some products both repel and kill. Many fly spray formulas also include synergists, which are additives that increase the effectiveness of the insecticides and repellents.
  • Understand pyrethrins, pyrethroids and the role of synergists. The most common insecticides in equine fly sprays are pyrethrins and pyrethroids. Pyrethrins provide a very quick knockdown, killing the insects quickly. However, pyrethrins are broken down rapidly by sunlight, so synergists—usually Piperonyl butoxide and/or Butoxypolypropylene glycol—are often added to protect and extend the effectiveness of the formula. 

Pyrethroids are synthetic forms of pyrethrins. The most common pyrethroids are permethrin, cypermethrin and resmethrin. Pyrethroids are not as easily broken down by sunlight, so they can remain effective for several days. Both pyrethrins and pyrethroids have a long track record for effectiveness and animal safety on horses and dogs.  

It’s important to note that while the active ingredients kill and repel the insects, the carrier or base or the formula contributes to the overall experience so it’s important to find a long-lasting fly spray with a base that is going to give you and your horse the best experience. While oil-based sprays may seem to be long lasting, they can leave an unpleasant oily residue. Water-based options can not only be long lasting, but also gentle on skin without the oily mess.

It is possible to get the best of both worlds – a long lasting, efficacious fly spray and a water-based formula. UltraShield® EX is the water-based fly spray that delivers proven fly control. Because UltraShield® EX is water-based and leaves no greasy residue and doesn’t attract the sun. This means you can count on UltraShield® EX to be:  

  • Moisturizing. Lanolin conditions your horse’s coat without greasy residue 
  • Long lasting. UltraBond® technology helps the formula securely adhere to the hair to extend repellency up to 17 days.  
  • UltraShield® EX kills and repels over 70 species of insects – including flies, ticks and gnats. 

This summer, UltraShield® EX has you covered! 


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