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What is Sweet Itch?

Sweet itch is the common name for what is scientifically referred to as Insect bite hypersensitivity (IBH) or Culicoides hypersensitivity in horses. It is caused by an allergy to insect bites, specifically bites of insects of the genus Culicoides1 commonly called midges. It is the most common allergic skin disease affecting horses1, occurring in all breeds, with a prevalence of 3–10% across Europe2 and ranges from 3% to 60% worldwide3. It is associated with the geographical distribution of Culicoides midges3. Sweet Itch is seasonally recurrent with the culprit insects being active during the spring, summer, and autumn.

Signs of Sweet Itch

Signs can include:

  • Rubbing against anything available including trees, stable doors, and fences
  • Excessive tail swishing to swat away midges
  • Raised, swollen areas of skin known as papules can develop1
  • Due to itching, skin can crust with dandruff production and hair loss1
  • Due to this severe itch, horses can cause skin trauma to the neck and rump by rubbing against trees and fences.
  • Lesions can be further exacerbated by secondary bacterial infections1 which can often require medical attention from a vet.
  • As the condition progresses skin can thicken, folds can develop and hair can become sparse1

Relief for horses with Sweet Itch

There is currently no cure for sweet itch although some progress has been made to develop Allergen-specific immunotherapy to varying levels of success2. As the condition recurs every year at the first contact with Culicoides midges, proactive management and control measures to reduce exposure to biting are important.
• Culicoides midges require water to thrive and are poor fliers so one of the simplest preventative measures to take is to move allergic horses to fields away from standing water. Avoid marshy, boggy fields near woods and standing water. Windy, well-drained fields are best. Another warm and moist environment loved by midges is on animal droppings! Therefore, keeping on top of mucking out and isolating muck heaps away from stables and grazing areas.
• Culicoides midges are reported to be most active from sunset to sunrise but in the middle of warm humid summers, they can be present all day, worsening at sunset. For this reason, it might be best to stable horses from dusk to dawn, especially in hot and humid conditions. Installation of fans in stables can also discourage midges!
• Horses can be covered in blankets or special sweet itch rugs to protect them from insect bites alongside frequent treatment with insect repellants, shampoos, and leave–on topical therapies3.
• Upon seeing affected skin, apply a topical barrier ointment, such as Copper Hawk Natural Animal First Aid, which contains ingredients known to soothe and moisturize.

Copper Hawk is a petrolatum-based infusion of 5 naturally occurring botanical extracts, including Yarrow, Gotu Kola, Common Plantain, Figwort, and Pau D’Arco. Individually these traditionally-used herbs have been seen to accompany accelerated healing of affected skin such as wounds, burns, and ulcers and support hair regrowth, while also having a natural scent that can prevent animals from licking the affected area. If you suspect your horse has Sweet Itch, you can purchase Copper Hawk Natural Animal First Aid on the Copper Hawk Online Shop.

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  1. Cvitas I, Oberhänsli S, Leeb T, Dettwiler M, Müller E, Bruggman R, Marti EI. Investigating the epithelial barrier and immune signatures in the pathogenesis of equine insect bite hypersensitivity. PLoS One. 2020 Apr 28;15(4):e0232189. doi: 10.1371/journal.pone.0232189. PMID: 32343720; PMCID: PMC7188278.
  2. Birras J, White SJ, Jonsdottir S, Novotny EN, Ziegler A, Wilson AD, Frey R, Torsteinsdottir S, Alcocer M, Marti E. First clinical expression of equine insect bite hypersensitivity is associated with co-sensitization to multiple Culicoides allergens. PLoS One. 2021 Nov 15;16(11):e0257819. doi: 10.1371/journal.pone.0257819. PMID: 34780496; PMCID: PMC8592417.
  3. Fettelschoss-Gabriel A, Birkmann K, Pantelyushin S, Kündig TM. Molecular mechanisms and treatment modalities in equine Culicoides hypersensitivity. Vet J. 2021 Oct;276:105741. doi: 10.1016/j.tvjl.2021.105741. Epub 2021 Aug 17. PMID: 34416400.
  4. https://commons.wikimedia.org/wiki/File:Culicoides_impunctatus.png
  5. https://commons.wikimedia.org/wiki/File:Dermatitis_on_pony.jpg
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