Sweet Itch Black Flies on Horses? Everything You Need to Know About Measures to Combat Them!

Black Flies on Horses? Everything You Need to Know About Measures to Combat Them!

For our horses, they are buzzing little pests: the so-called black flies. Find out why these tiny insects are not only a nuisance, but also a considerable danger for horses in our guide.

What are black flies?

Many horse owners probably feel an itch just hearing the word: Black flies! But what are black flies and why do they make life so difficult for our beloved horses? Black flies have inhabited the earth since at least the Jurassic period and there are now around 2,000 different species. Perhaps the blackfly already tormented the dinosaurs.

The insects are only a few millimeters in size and are particularly active in summer: they harass our horses in the morning and evening hours. More than 50 species are widespread in Germany. Along with gnats, horseflies and mosquitoes, black flies are the main cause of the unpleasant summer eczema. Especially in older and immunocompromised animals, the allergic skin disease can become problematic.

Why are black flies dangerous for horses?

Nobody likes mosquitoes. When we humans think of the little insects, the first thing that comes to mind is unpleasant itching and annoying buzzing. However, the slight itching and redness after a mosquito bite usually subside after a few days and are relatively harmless. Black flies are different: they don’t bite blood vessels directly like mosquitoes do, but bite. And their favorite victims are grazing animals. Black flies are particularly prey on our horses. With their mouthparts, they tear a small wound in the horse’s skin. This wound fills with blood, which the black flies suck up with their proboscises. This is why the blackfly is also called a pool sucker.

The danger to the horse is often underestimated. The bite of the blackfly is unpleasant and painful for horses and represents a health risk. Black flies release a salivary secretion into the local bite site to allow blood to pool. The saliva dilutes the blood and can cause significant reactions in the warm-blooded horse. The consequences of this are manifold: from mild itching to severe allergic skin irritations to – in extreme cases – cardiovascular failure, the bites can have dire effects. Horses react very individually. Icelandic horses, for example, are considered particularly sensitive.

If you do not protect your horse sufficiently from this danger, the black flies can cause severe allergic symptoms. In the event of a mass attack by the pests, the horses may also try to flee in a panic, which can sometimes cause them to have an accident.

Popular attack points of black flies are, for example, the hose of the stallion or gelding, the ears or the abdominal seam.

How do black flies cause sweet itch in horses?

As mentioned above, some horses are allergic to the foreign substances in the blackfly’s salivary secretions. They release histamine, which leads to severe itching, swelling and redness. The quadrupeds start scratching and chafing as the itching is unbearable. Secondary bacterial infections with purulent inflammation are often the result. A vicious circle begins, which in many horses leads to the so-called “summer eczema”, but which is also triggered by other insects such as midges, mosquitoes or horseflies.

The affected horses have developed a hypersensitivity to a certain protein in the salivary secretions of black flies. What exactly causes this allergy has not yet been completely clarified. However, it is important that you recognize the symptoms early to prevent the change to eczema. Only then can you end your horse’s suffering early.

What are the symptoms of sweet itch in horses?

If you notice the following symptoms in your horse, you should react and take action:

Severe itching


Bald skin due to constant rubbing

Rash Thickening of the skin

Crusting Scaling

Bloody and oozing wounds

Impairment of the general condition

Look primarily for small pustules especially on the mane crest, ears, tail rump and belly seam when you ride out with your horse in the summer or when it is pasture time. After a few hours, the bites become unpleasantly itchy. Even if you haven’t spotted a rash, be alarmed if your horse is suddenly very restless and rubbing hard. Now is probably the time to actively combat the black flies that help trigger the allergic skin condition.

TIP: If you suspect sweet itch in your horse, you should urgently present him to the veterinarian. The exact diagnosis of the veterinarian is inevitable, because the symptoms can also be other skin diseases. Other diseases, caused for example by fungi or parasites, show similar symptoms. The medical doctor can differentiate based on his expertise.

What helps against black flies in horses?

In order to avoid an itchy and unpleasant allergy of the skin caused by black flies or other insects, you can take helpful precautionary and protective measures. These measures start with hygiene. Clean out your horse’s stall thoroughly every day and disinfect the stable floor regularly.

NOTE: To find out how to muck out your horse’s stall properly, read our guide “Mucking out horse stalls properly – not so much manure!

Of course, you should also regularly clean horse troughs and feed troughs for horses and remove food residues. Sweet carrot and apple residues provide perfect conditions for insects of all kinds. By the way, you can wash out troughs and watering troughs with vinegar or lemon juice – insects don’t like that at all. However, the acidic smell also has a repellent effect on some horses.

Especially in summer, the four-legged friends spend a lot of time in the pasture. You should also regularly clear the pasture of horse droppings – for example, with practical manure boys. This prevents the annoying mosquitoes from spreading so quickly. The manure pile should be placed far away from where the horses are staying.

Dry puddles and mud in the pasture with sand, as damp spots also attract mosquitoes. You should also provide your horse with retreats in the pasture. A mobile shelter or groups of trees offer some protection from pesky flies and mosquitoes.

What else can you do against black flies on horses?

Keep insects out of the stall by lining the stall windows with fly screens or mesh panels. Set up electric fly killers to repel mosquitoes as well. Devices that work with UV light and electricity have proven effective in the horse barn.

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