Fly Repellent for Horses

Fly Repellents are one of the 10 Solutions to Horse Flies.

Biting and blood sucking insects rely mainly on smell to find their prey (such as horses and us). Although other senses (e.g. sight) may be used to varying extents (depending on the type of insect), they rely mainly on smell. The various types of repellents (chemical, organic or natural) work by releasing strong scent molecules, which confuse the insect by mixing in with and masking the smell of the horse, so they are unable to home in on the smell of the horse. Trying to find their victims through these added smells is like us trying to see a distant object through fog.

The term 'repellent', although commonly used, is misleading as these products do not repell the insects so much as confuse their sense of smell. Although the flies may eventually leave, it is not because they were driven away by the smell, but rather they simply moved on as they could not find they way to their prey due to the additional smells produced by the 'repellent'.

This article includes the following topics:

  • 1.0 Natural Repellents
  • 2.0 Home-made Repellents
    • 2.1 Cautions about Home-made Repellents
    • 2.2 Home-made Repellent - Garlic Recipe
    • 2.3 Home-made Repellent - Cider Vinegar
    • 2.4 Home-made Repellent - Essential Oil Recipe
  • 3.0 Chemical Repellents

1.0 Natural Repellents

As repellents work by producing smells which mask or overwhelm that natural smell of the horse, repellents made from natural ingredients need to have a strong smell in order to work. For this reason, they are made from plants which have a strong natural smell, such as:garlic, lavender, cedar, rosemary, eucalyptus, cinnamon or tea tree.

Most natural repellents are sprayed onto the horse. However, some types of repellent (e.g. garlic) can be added to the horse's food, and are secreted by the horse along with skin oils. These are also known as 'internal repellents' as they are taken internally rather than sprayed onto the outside of the horse. Although garlic is a well-known and accepted product for this purpose, most repellents cannot be administered internally and could make a horse extremely ill, so one should not use any product in this way (even if natural and organic) unless it has been approved for this purpose.

There are a number of commercially available products based on natural ingredients. One can also make repellents oneself based on natual ingredients.

2.0 Home-made Repellents

Many people use natural ingredients to make their own sprays. As long as one sticks to basic ingredients (e.g. water and essential oils), this should be safe for external use on the horse. However, see section 2.1 below for some cautions.

Do not add perfume to your repellents. Based on the fact that repellents work by emitting smell molecules, some people use perfume on the basis that it is strong smelling. Unfortunately, this usually has the opposite approach, as many insects can use the smell of the perfume to home in on your horse (or you). Consequently, all use off perfume should be avoided.

Many recipes are based on water and essential oils. However, oil does not mix well with water, so one normally adds a small amount of washing up liquid (dish washing liquid) to the mixture, to break up the oil so that it mixes better with the water. Even so, one should give such mixtures a good shake just before spraying them.

Experience with homemade repellents varies. Some people swear that they are as good as the commercial chemical products, while others find them useless. Certainly, experience shows that they do not have the same consistent performance as the commercial chemical versions. However, they are much more natural and as such likely healthier for you and your horse. Furthermore, the homemade repellents are generally much cheaper than the commercial versions. Given these two major advantages, it is worth giving them a try.

Note that the effectiveness depends largely on the type of insect. For one insect a given essential oil may work well while for another a different essential oil may work better. Consequently, when testing the effectiveness of different oils, one may need to change depending on the type of insect which is prevalent at the time. It is for this reason that some recipes call for several different oils, to effectively repel different types of insects.

Below are some popular recipes. One can find additional recipes at Herbal Insect Repellents.

2.1 Cautions about Home-made Repellents

When using homemade repellents, some cautions to keep in mind:

  • Be careful not to spray saddles, tack or clothing in case that they may stain.
  • Do not get the spray into the eyes or nostrils of the horse.
  • Check the skin and coat of the horse after use to ensure that the horse does not have an allergic or other negative reaction.

Note that we take no responsibility for any of the information on this page. Use are your own risk; if in doubt discuss with your veterinarian before use.

2.2 Home-made Repellent - Garlic Recipe

Garlic is one of the strongest and most popular ingredients for organic repellants. It can be used internally or externally.

To use as an external spray:

  • Mix 1 part crushed garlic to 5 parts water. Leave overnight.
  • Strain out the garlic and put the liquid into the spray bottle.
  • Spray on the repellant as normal.
  • The garlic in the spray will keep for only a short time before it starts to go off. To preserve for longer, keep the spray in a cool and dark place (e.g. refrigerator).
  • Be careful about contact with saddle, tack or clothing as in some cases this could result in staining.

The downside of this recipe is that the strong smell of the garlic can be unpleasant. 

Warning: read section 2.1 before use.

2.3 Home-made Repellent - Cider Vinegar Recipe

Use as an external spray:

  • 1/3rd Cider Vinegar (if you don't have cider vinegar, use white vinegar)
  • 1/3rd Avon SkinSoSoft Bath Oil
  • 1/3rd Water
  • One drop washing up liquid (dishwashing liquid), so that the oil mixes with the other ingredients.

A popular variation of this recipe is to add a few drops of essential oils, with citronella oil being the most popular.

The pleasant smell of the oil tends to offset the sharp vinegar smell, resulting in an odour that is not unpleasant.

Warning: read section 2.1 before use.

2.4 Home-made Repellent - Essential Oil Recipe

There are a large number of recipes based on essential oils or oil-based scents. The base ingredients include lavender, cedar, rosemary, eucalyptus, cinnamon, citronella and tea tree. Although there are many different variations, most of them can be summed up as:

  • Fill a small spray bottle with water.
  • Add several drops of essential oil. One can use just a single oil, or a number of different oils.
  • Add a couple of drops of washing up liquid (dishwashing liquid), so that the oil mixes with the other ingredients.
  • Shake well just before using.

One can experiment with different oils or combinations of oils to see what works best for you.

Some people use a mixture of white vinegar and tea, instead of water.

Warning: read section 2.1 before use.

2.4 Internal Fly Repellents

There are a number of fly repellants which one can add to the food or water of the horse. These work by changing the smell of the horse, or by changing the PH of its blood (so that insects don't want to drink it), or a combination of the two. Since these changes take time, one needs to feed the ingredients for approximately a week before one sees improvements.

One common additive is garlic, which is usually added to the food in fresh or in dry powdered form. Note that some horses dislike garlic and will go off their feed if garlic is added. One should start by adding very small amounts until the horse gets used to the taste. One also needs to check that the horse is still eating its food, rather than leaving it or throwing it on the floor, to ensure that the garlic addition is not affecting its feeding.

Other common additives are white wine vinegar or cider vinegar, added to their drinking water. This should be done in small amounts (e.g. 1/4 cup or 50ml per horse, per day). One needs to ensure that these additions do not result in the horse drinking less water, as that could have serious medical consequences (e.g. increased risk of impaction colic).

Discuss with your veterinarian any changes to the horse's feeding regime, prior to making such changes.

3.0 Chemical Repellents

There are about a douzen different chemicals which are used in insect repellents. Some commercially available products use one chemical, some another, and many a combination of chemicals.

The advantage of the chemical repellents over natural repellents include:

  • Chemical repellents tend to me more effective, over a wide range of different types of biting insects.
  • Chemical repellents tend to be effective for a longer period of time.
  • Chemical repellents can be stored for long periods of time.
  • The performance of chemical repellents has been well researched and documented.

Against these advantages, there is increasing concern about the potential heath risk to horses and people associated with the frequent or high-dosage use of these products. Research has shown that when these chemicals are sprayed on human skin, over half of the product is absorbed into the skin, with a substantial portion entering the bloodstream and organs. Furthermore, research is increasing demonstrating that there are various health risks associated with the chemicals. Consequently, if you frequently come in contact with these chemicals (e.g. using bare hands to apply them around sensitive eyes and mouth areas), there may be long-term health risks to yourself. Furthermore, although the amount of chemical which enters the horse will be a lower percentage than for people (as much remains on the coat rather than penetrating to the skin), there are increasing concerns about the potential health implications for the horse of long-term use. In general, the more effective chemical repellents are the ones that have a higher percentage of active ingredients (higher percentage of chemicals), so the most effective repellents also tend to be the ones with the highest health risk.

The other major disadvantage is cost. Over the duration of the insect season, the cost of repellents can be substantial.