Sweet Itch In Horses

What causes Sweet Itch?

Sweet Itch or IBH (insect bite hypersensitivity) is a skin condition affecting horses and other equine, including asses and zebras.

The condition is caused by an allergic reaction to a bite from biting flies, most commonly Culicoides midges.

Specifically, when a horse is exposed to the saliva from biting insects, it can trigger an strong immune response. An increase in histamine travels to the affected areas and can cause the skin to become itchy and inflamed.

The actual inflammation from the bite itself does not cause the severe skin condition, but the discomfort caused by the bite can cause the horse to rub or bite the area which can lead to an infection and a spread of the condition.

The severe itching caused by the bite, also known as Pruritus, can result in a mixture of skin conditions including bald patches, loss of tail and mane hair, broken hairs, broken and bleeding skin and open sores.

How common is Sweet Itch?

Not all horses will be affected by it. It’s thought around 5% of the UK’s equine population is currently affected. Some horses can be more sensitive to the Culicoides midges than others. Seemingly different breeds of horses react in different degrees to these biting flies. For example, up to 30 percent of Friesian horses are affected, as are Icelandic ponies and Haflingers, whereas Sweet Itch is rare in English Thoroughbreds. However all breeds of horse can be affected by the condition.

What age does Sweet Itch start?

Horses that go on to develop Sweet Itch generally show signs of the condition from four years on, and the condition tends to get more severe as the horse ages.

How serious is Sweet Itch?

Sweet Itch is very treatable (see treatments and cures below), however as a horse owner it’s important that you familiarise yourself with the symptoms of Sweet Itch so that you can identify the condition as soon as possible.

Sweet Itch, and the self inflicted trauma involved, can cause a huge amount of pain and discomfort for the affected horse so it’s important the condition is treated immediately.

When to look out for Sweet Itch

Horses are much more likely to develop symptoms of Sweet Itch during the warmer months,  around April to late October, when the Culicoides midges population peaks.

Although, as a result of climate change, it is possible for horses to develop Sweet Itch during traditionally colder months and therefore the condition shouldn’t be ruled out if symptoms show during the winter.

Ways to prevent Sweet Itch

Unfortunately once a horse has developed the skin condition, there is a high chance of it recurring every year. Being prepared before the season starts and reducing exposure to Culicoides midges is the best prevention.

Culicoides populations tend to exist in boggy, marshy fields. If a horse has a history of Sweet Itch, they should be grazed in exposed, windy fields or chalk-based farmland wherever possible. Any grazing land should be well drained and the horse should be kept away from any areas with a high population of flies.

Horses can be protected with light summer rugs or fly rugs, which protect the areas of the horse most likely to be bitten.

Here are a few of our favourite summer rugs:

Rambo Fly Buster Vamoose

Get your Rambo Fly Buster Vamoose here >

Rambo Fly Mask Plus Vamoose


Get your Rambo Fly Mask Plus Vamoose here >

Masta Avante Fly Mesh Combo

Get your Masta Avante Fly Mesh Combo here >

Amigo Aussie Allrounder

Get your Amigo Aussie Allrounder here >

At night, when midges are at their most active, stabling the horse can help protect them from getting bitten. Stables should be protected with fine mesh screens, and installing ceiling fans will provide a breeze to stop flies from landing on the horse.

Stables should be kept clean and free of manure and standing water, as these provide the best conditions for insects to breed.

Fly repellents can be very effective in driving away flies and midges away from a horse to reduce the risk of biting. Fly repellents come in various forms including gels, creams, wipes and sprays.

These are some of our favourite fly repellents:

NAF Off Citronella Fly Spray

Get your NAF Off Citronella Fly Spray here >

Carr & Day & Martin Equimist 360 Natural Insect Repellent

Get your Carr & Day & Martin Equimist 360 Natural Insect Repellent here >

Barrier Healthcare Super Plus Fly Repellent

Get your Barrier Healthcare Super Plus Fly Repellent here >

Insecticide solutions containing Benzyl Benzoate can also be an effective preventive treatment for horse prone to Sweet Itch.

Carr & Day & Martin Killitch Sweet Itch Solution

Get your Carr & Day & Martin Killitch Sweet Itch Solution here >

Some fly repellents and insecticides are irritants and should therefore not be used on a horse’s skin if it is already broken, or if there is severe hair loss. Be sure to check this when deciding on the best repellents for your horse.

Identifying Sweet Itch

The most common symptoms of Sweet Itch in horses include severe itching, hair loss and dandruff. Where the biting has occurred the area may become inflamed, and in more serious conditions, horses may develop sores which may weep and become infected.

Midges usually feed along the top of the horse, including the back, head, mane, rump and tail. Extra focus should be given to these areas, however in more sever cases the condition can spread across the body and even reach the underbelly.

A horse affected with Sweet Itch will show visible signs of scratching including rolling, scratching their mane with their hooves and biting at their skin. Horses with Sweet Itch may also use objects to scratch themselves; trees, fences and stables. This kind of behaviour will increase the risk of infection and therefore it’s important that any horses with Sweet Itch are treated as soon as possible to prevent the condition from worsening.

Some horses may react to other allergies in the same manner as bites from Culicoides midges, so further testing may be required to determine whether the allergy is being caused by insects or other environmental factors.

How to cure Sweet Itch

If you suspect your horse is suffering from Sweet Itch, you should call your vet who will confirm this for you. They will then recommend the best treatment. Many allergies can cause similar symptoms so it’s important not to make assumptions.

If a horse has developed Sweet Itch, it’s important to try to stop the horse from being bitten again. Horse rugs can prevent the condition from worsening as a result of the horse irritating the bite by rubbing or biting.

Rambo Hoody Fly Rug

Get your Rambo Hoody Fly Rug here >

Rambo Protector Fly Sheet

Get your Rambo Protector Fly Sheet here >

Sweet Itch can be treated by a vet with an injection or tablet containing corticosteroids. Corticosteroids depress the immune system so that any midge bites cause a less severe reaction or no reaction at all.

Antihistamines can provide some relief, however these have the potential to make horses drowsy.

Some lotions, including Sudocrem, can help to bring some relief and reduce inflammation in the affected areas.

Thanks to new research in Iceland, an experimental vaccination for Sweet Itch may become available in the next few years. The new vaccine would only be effective on horses that have not yet been exposed to the allergen (the insect saliva). Therefore horses that already suffer with the condition would unfortunately not benefit from this vaccination.

How long does Sweet Itch last?

The length that the horse is affected really depends on how effective treatment is. The earlier a horse is treated, the more likely it is that the severe symptoms (such as infected sores, hair loss and skin wrinkling) can be avoided.

Remember that once a horse contracts the condition, they will be at serious risk of a repeat infection every year. It’s necessary to be extra vigilant and to action any preventative treatments early enough in the season.


Sweet Itch: Wikipedia

Equus: Wikipedia

Ceratopogonidae: Wikipedia

Horse & Hound: Sweet Itch in horses

Horsemart: How to prevent Sweet itch

Moray Coast Vet Group: Sweet Itch

Lip Hoop Equine Hospital: Sweet Itch PDF

The British Horse Society: Sweet Itch Leaflet

The Horse: Is an equine IBH vaccine on the horizon

Equine News: Insect Bite Hypersensitivity

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