Sweet Itch in Horses: Causes, Symptoms, and Effective Treatment Options

What is sweet itch in horses?

Sweet itch is one of the most common allergic skin conditions in equine medicine. In Icelandic horses in particular, an allergy to proteins in the saliva of various biting insects is especially common, but in principle horses and ponies of all breeds can be affected. The insects are mainly active from April to October during the morning and evening hours, especially near bodies of water.

How does sweet itch develop in horses?

Sweet itch is an allergic skin condition caused by an overreaction to proteins in insect saliva—especially from black flies. After an insect bite, these allergens trigger a strong immune response, leading to itching and inflamed skin, particularly around the mane, tail head, belly, and head. Some horses, especially Icelandic horses and Shetland ponies, are genetically more susceptible. Exactly why this overreaction occurs in some horses and not others is not yet fully understood. Environmental factors such as protein-rich pasture, stress, and a weakened immune system can further intensify sweet itch symptoms.

A black fly bite often leaves a red, swollen, intensely itchy patch of skin. The itching can last for several days, and the affected areas tend to become increasingly inflamed due to constant rubbing. A black fly bite is not only uncomfortable for horses—it can also increase the risk of secondary infections if the skin is rubbed raw.

What does sweet itch look like in horses?

The first signs of sweet itch usually appear as a response to intense itching. Once visible rubbed areas and skin thickening can be seen, the horse has generally already been bitten. The following symptoms may indicate sweet itch:

• Skin rash in the form of pustules
• Intense itching, leading to restlessness and frequent rubbing
• Bald patches caused by excessive rubbing
• Thickened skin and crusting
• Open, bleeding areas and weeping sores
• Secondary infections caused by bacteria or fungi that can easily enter damaged skin
• Papules (small, pinhead-sized bumps under the skin)

Constant rubbing worsens the skin damage and increases the risk of infection. In advanced stages, the skin can become thickened, dry, and wrinkled, and the horse may lose a significant amount of hair. At that point, the horse often can no longer be ridden.

Diagnosis and differentiation from other skin conditions

If these symptoms occur, a veterinary examination is essential. Sweet itch can easily be mistaken for other skin conditions caused by fungi, parasites such as mites, lice, or biting lice, or infections with the pinworm (Oxyuris equi). These conditions can produce similar symptoms, ranging from mild itching to severely rubbed, sore skin.

What helps against sweet itch in horses?

What truly helps with sweet itch varies from horse to horse. While some horses respond well to conventional treatment methods, others may benefit from alternative approaches. Below you’ll find an overview of the available treatment options and whether a sweet-itch vaccination can make sense.

Treatment with conventional methods

The main goal of treating sweet itch is to relieve symptoms. Without treatment, the horse will continue to rub, which can lead to significant skin damage and secondary infections.

At the beginning of a flare-up, veterinarians often use glucocorticoids, administered either intravenously or intramuscularly. These medications reduce the allergic immune response and quickly relieve itching. As treatment progresses, they are typically switched to oral preparations.

Coat and skin care plays a crucial role in treatment. It is important to remove dirt and crusts regularly using a saline solution. Zinc ointments can support healing of inflamed and weeping skin. If bacterial infections are present, antibiotic therapy is necessary and must be initiated by a veterinarian. In addition, special shampoos can help reduce itching, while aloe vera—applied topically or added to feed—may support skin recovery.

Recommended products for treating sweet itch in horses:

• 99% pure aloe vera gel for skin and hair
• 0.9% saline solution
• Zinc ointment

Alternative treatment methods

Alternative remedies are becoming increasingly popular in the management of sweet itch. Many owners choose a holistic approach and often use homeopathic remedies such as Sulfur, Echinacea, Ledum, Staphisagria, Graphites, and Cardiospermum. Schüßler salts are also used, for example Calcium phosphoricum D6 and Natrium chloratum D6 for dry eczema, as well as Calcium fluoratum D12 for wounds, cracks, and crust formation.

New vaccine technologies

The first test results of an innovative vaccine technology are promising. Horses treated with the new sweet-itch vaccine showed good tolerance of the active ingredient and a reduction in tissue damage caused by allergic reactions. In one study, Icelandic horses—who are not exposed to the allergy-triggering biting midges in their home environment—were imported to Switzerland and treated there with the novel vaccine. These findings raise hope that vaccination could one day protect horses worldwide from sweet itch.

In addition, the active ingredient Insol, which is primarily used for fungal diseases, is considered promising for improving sweet-itch symptoms. Vaccination with Insol is administered before the insect season and repeated two to three times. It is advisable to discuss with your veterinarian whether vaccination with Insol is an option for the affected horse.

Protective measures and recommendations

Until vaccines become widely available, it remains important to protect affected horses from the insects that trigger the condition, adjust feeding, and optimise management conditions. Horses with sweet itch are often particularly sensitive, so their increased susceptibility should be taken into account. The good news is that symptoms can be managed with appropriate therapy and may decrease over time. Early action at the first signs, however, is crucial to safeguard the horse’s wellbeing.

Preventing sweet itch: 5 tips to help avoid sweet itch in horses

The underlying condition—an allergy to components of insect saliva—cannot be cured. However, various measures can make summer much easier for horses with sweet itch. Here are five tips to help you and your horse steer well clear of sweet itch.

Optimise turnout times

It is crucial to minimise contact with biting insects as much as possible. The period from 10 a.m. to 4 p.m. is considered the time when insects are least active and therefore the best turnout window for sweet-itch horses. Areas near bodies of water, manure heaps, and leftover feed should be avoided, and there should always be access to an insect-free shelter or stable. Sprays or lotions for insect deterrence are not equally effective everywhere or for every horse.

Use sweet-itch rugs

Sweet-itch rugs provide reliable protection against bites from female biting insects on sensitive areas of skin. The rugs must fit well to avoid rubbing, and only consistent use ensures effective, long-lasting protection from these pests. Many affected horses experience complete symptom relief simply from wearing the rug.

Adjust feeding for sweet-itch horses

🎥Video tip: Feeding sweet-itch horses correctly! Learn how to optimise your horse’s diet to support skin and coat and relieve itching effectively—for greater day-to-day wellbeing.

Although the feed industry offers a wide range of supplements for “sweet-itch horses,” sweet itch unfortunately cannot be cured with feed additives. However, the supply of minerals and trace elements should be reviewed and optimised—especially in horses with skin conditions. Many horses show an improvement in symptoms when starch- and protein-rich feeds are reduced. A basic review of the ration is therefore an important part of therapy, as improved metabolic function can help relieve symptoms. Learn more about proper horse feeding.

4. Use insect-repellent products

There are numerous products on the market that can be applied topically. They are intended to care for affected areas of skin, protect against insects, and support healing. The same applies here: not every product works equally well for every sweet-itch horse. It is often necessary to try different products, which is why some manufacturers offer sample packs.

Hygiene is crucial when treating the skin locally. Residues from care products should be washed off at least once a week with a mild shampoo to give the skin time to dry. It is essential to wear disposable gloves when applying these products to avoid constant skin contact with the preparation and the affected skin.

5. Consider the location of stable and pasture

🎥Video tip: Insect-free in the stable! In the USEF Learning Center powered by ClipMyHorse.TV, Hope Hobday Glynn explains simple measures to reduce insects around the stable and pasture—for more comfort for you and your horse!

To minimise the risk of sweet itch in horses, choosing the right stable location plays a crucial role. Horses that are prone to sweet itch should not be kept near bodies of water, manure heaps, or leftover feed, as these strongly attract insects—especially mosquitoes. Such areas provide ideal breeding sites for the insects that can trigger flare-ups. A stable fitted with fly screens on doors can also help keep insects out. Shaded areas, such as hedges or trees, should give the horse places to retreat and protect itself during the day. An open barn system or an insect-free shelter also offers important protection from insect bites, especially during peak insect activity in the morning and evening.

Sweet itch in horses: summary

Sweet itch is a challenging skin condition that can severely affect a horse’s wellbeing. Early recognition of symptoms and targeted treatment are essential to relieve itching and prevent serious skin damage. Both conventional and alternative treatment methods can help manage symptoms and improve the horse’s quality of life. At present, there is still no widely available vaccine against sweet itch, but promising developments in research offer hope for future progress.

Until then, it remains important to take protective measures against insect bites, optimise feeding and management conditions, and follow individually tailored care and treatment strategies. With a comprehensive approach and the right support, sweet itch symptoms can be successfully managed and the affected horse’s wellbeing maintained.

Sweet itch in horses: the most important questions and answers

What is a “sweet-itch horse”?

A “sweet-itch horse” is a horse that suffers from sweet itch—an allergic skin condition triggered by bites from certain insects, especially Culicoides biting midges. This allergy leads to intense itching and skin damage because the horse rubs excessively.

When is a horse considered a sweet-itch horse?

A horse is considered affected when it shows sweet itch symptoms over longer periods, such as intense itching, rashes, crusting, and hair loss. Diagnosis should always be made by a veterinarian to rule out other skin conditions.

How can I relieve my horse’s itching?

To relieve itching, special shampoos, aloe vera gel, or healing ointments can be used. Glucocorticoids prescribed by a veterinarian can also reduce itching. Regular cleaning of affected areas and preventing insect bites are also important.

Is there a vaccine against sweet itch?

There is currently no officially approved vaccine against sweet itch, but early test results from an innovative vaccine technology are promising. Research is ongoing, and market availability may follow in the coming years.

When will a sweet-itch vaccine be available?

It’s difficult to give an exact date, as vaccines are still in development. Early studies are encouraging, but it may take several more years before a vaccine is widely available.

What should I do if my horse has sweet itch?

If your horse has been diagnosed, take steps to reduce insect bites—for example by using insect repellents and sweet-itch rugs. Targeted coat and skin care, as well as a suitable diet, can also help. In severe cases, veterinary treatment with medication is necessary.

What feed is suitable for sweet-itch horses?

A balanced diet with high-quality, as natural as possible ingredients is recommended. Feed rich in omega-3 fatty acids may help reduce inflammation. Sugary or high-starch feeds should be avoided. A muesli for sweet-itch horses should be low in sugar and starch and rich in omega-3s. Special feeds for sensitive horses are available—when in doubt, consult an expert or your veterinarian.

What helps with weight gain in sweet-itch horses?

To help an underweight sweet-itch horse gain weight healthily, the diet should include easily digestible fibre and high-quality fats. Suitable feeds provide moderate energy, low sugar and starch, and healthy oils such as linseed oil.

Is garlic good for horses with sweet itch?

The effectiveness of garlic for sweet itch is debated. While some owners report that it acts as a natural insect deterrent, others find it can cause stomach issues. Garlic should therefore be fed cautiously and only after consulting a veterinarian.

Is sweet itch curable in horses?

Sweet itch is usually not completely curable, but symptoms can be significantly relieved and controlled with appropriate treatment and care. Early measures and consistent management can help improve the course of the condition.