The 6 Best Fly Spray and Repellents for Horses, According to Experts

What to Look for in a Horse Fly Spray or Repellent

Application 

Before applying any product to your horse, it’s important to read the label thoroughly, as the chemicals in fly spray often have limitations, with instructions that will tell you how to avoid irritating sensitive skin or contaminating water and food. 

While the method of application will vary, most spray or topical pest management solutions are best applied after bathing and brushing the horse, so the product can be applied to a clean, dry coat for maximum efficacy. 

When using a product for the first time, begin by applying to a small patch of your horse’s skin to test if they demonstrate skin irritation or other reactions. 

Depending on the product’s instructions, you’ll probably need to spray it on, towel it on, or massage it in like shampoo, then rinse. Shake the bottle well before use. Place an emphasis on the head, neck, back, chest, legs, and withers when applying to your horse, as these areas are most pests’ favorite biting regions. Some prefer to start with the legs and spray up from there, so as to minimize the chance of startling your horse. Allow your horse to move as needed to feel comfortable while being sprayed. When using on the face, remember to apply the product to a cloth and rub it in to avoid getting in their eyes. Never apply to the animal before tacking in order to avoid irritation in the saddle area. 

When using a spray, adjust the nozzle to a stream and apply gently. Some sprays direct you to brush the product into the coat after spraying on. Roll-on products, creams, and other forms of pest repellent should be used as directed. Reapply at the interval instructed on the label. 

Most Common Pests

Pests most commonly attracted to horses include black flies, horse flies, deer flies, mosquitoes, gnats, and face flies. Stable and house flies are also frequently found in horse facilities, irritating to horses as well as other livestock. Although some pests share commonalities, each type has its own unique characteristics. Here is a bit about the most common horse pests:

• Face flies: Feed with spongy mouth-parts only around the animals’ face, particularly the nose and eyes; capable of transmitting eye-worms. This fly requires fresh cow manure for egg-laying and larval development.
• Black flies: Lay eggs in or near clean water; attack horses around the face—primarily focusing on the ears. Their bites are very painful. 
• Horse flies: Known for their remarkably large eyes, these big biters are able to fly very fast. Their mouth parts are scissor-like and cut holes in the tissue they bite. They prefer to grow their larvae in aquatic settings, and as such are more often encountered near a water source.
• Deer flies: Deer flies are smaller than horse flies, with dark stripes. However, their bloodsucking bite is similar, and typically both types of fly can be addressed with the same repellent.
• Gnats (also called biting midges): Also called no-see-ums, these tiny creatures also prefer breeding areas near water. Can cause irritation, allergic reactions, and swelling where they bite. 
• Mosquitoes: Larvae develop in standing water or partially aquatic areas; can transmit several strains of encephalitis, West Nile Virus, and Eastern equine encephalitis (EEE) which causes serious neurological disruption in horses; most often (but not always) active and feed at night.
• Stable and House Flies: both prefer moist, decaying organic matter for laying their eggs. Both fly varieties can transmit harmful nematode parasites to horses.

Oil or Water Base

Generally speaking, oil-based products tend to contain more chemicals but also remain effective longer than water-based ones. This is usually because water-based products rinse off more easily in water and sweat than oil-based ones do. 

The downsides of oil-based products are the unpleasant oily residue they leave behind, the way they can dry out horses’ skin and lead to burning (similar to humans with suntan oil on) as well as their tendency to collect dust and dirt. Some horses experience irritation of the nose, throat and/or lungs from oil-based repellents too. 

Duration 

Fly spray products vary in duration of effectiveness for several reasons. For starters, the environment and activity level of your horse can play a role. Humidity, rain, and sweat all impact duration, while moisture and heat are often attractive to egg-laying insects making them prone to return quickly. Product constitution is also a factor, with some sprays only working for a few hours before requiring re-application and others remaining effective for up to two weeks or longer. 

Products with an oil foundation generally last longer than water-based ones. Those with essential oils or other natural ingredients may not have a clear duration listed on the label (for example, some may have vague instructions like “apply liberally” and “reapply as needed”), so you’ll need to play it more by ear with those. 

Part of this variation is due to the way the products break down when exposed to UV light and oxygen. Chemical or synthetic ingredients take longer to break down, making them last longer than natural options that require more frequent application. Efficacy and duration can also vary depending upon whether the product simply repels pests or both kills and repels them. 

Why Trust The Spruce Pets

This article was researched and written by KJ Callihan, a writer for The Spruce, who has worked in animal shelters, where she helped socialize animals for adoption, and fostered animals of various kinds. She also writes for CNET, AAA Northeast magazine, and more,

To direct our research for this story, we consulted Sarah Farley, University of Illinois’ Local Food Systems and Small Farms Extension Educator. Farley provides expert assistance to small farmers regularly through her degrees in Animal Sciences and Agribusiness Management in addition to her experience in livestock and crop production and agricultural entrepreneurship. We also spoke with Paula Hitzler, Michigan State University’s Horse and Teaching Research Manager,  Tracy Rowe of Rowe Stables, LLC,  in Okemos, Michigan, as well as Julie Schultz, a horse owner with a background in Equestrian Science from William Woods University.