Horse Sweet Itch

Information on biting midges, no see ums & flies that cause sweet itch in horses.

biting midges cause sweet itch in horses

Select a Topic

  1. What is Sweet Itch?
  2. What Causes Sweet Itch?
  3. Diagnosing Sweet Itch
  4. Help for Sweet Itch
  5. More Information on Sweet Itch

What is Sweet Itch?

Sweet itch is essentially an allergic skin condition. It is caused by a hypersensitivity reaction to the bite of the Culicoides midge and also certain horse flies. Certain horses are overly sensitive to the saliva of these pests and irritation and intense itching occurs at the site of the bite. Self- inflicted damage will occur as the horse scratches himself.

Signs and symptoms of Sweet Itch
  • Intense skin irritation in the mane and tail regions of the horse
  • Irritation in the summer months
  • Itching and discomfort in the early morning and late afternoon
  • Restlessness
  • Intense rubbing against trees or fences
  • Swishing of the tail
  • Damage and swelling or wounds around the horses ears, poll, mane, withers, rump, and tail head (less common around the horse’s face, chest, and belly)
  • Hair loss over the affected area (often the mane and rump)
  • Bald, red, inflamed skin, that may have crusting and sores
  • Chronically thickened, blackened, and wrinkled skin
  • The bites cause a local allergic reaction with the development of papules and pustules


What Causes Sweet Itch?

The saliva of the midge is the principle culprit. Apart from Culicoides midges other fly and parasite species have been associated with similar hypersensitivity reactions including the stable fly, horsefly and the black fly, as well as no see ums. Some horses may have a genetic predisposition to the disease. Conditions related to intense itching may also include lice infestation, chorioptic mange, rain scald, ringworm, food hypersensitivity and dermatitis.

Diagnosing Sweet Itch

If you notice the signs outlined above, it is important to get a proper diagnosis of sweet itch from your vet. Your vet may decide to take a skin biopsy or carry out some intra dermal skin allergy tests to make a definitive diagnosis of sweet itch.

Help for Sweet Itch

Corticosteroids remain the most useful product for treating and controlling the skin allergy caused by midge bites and other pesky bugs such as gnats and parasites. However with all usage of corticosteroids they can increase the risk of inducing laminitis in the horse. As steroids do have side-effects in horses, they must only be prescribed by a vet – they are very potent anti-inflammatories that may stop the itching and allow the skin to heal, but may also cause side effects. Anti-histamines are used but results are not guaranteed.

More Information on Sweet Itch

Tips related to Sweet Itch
  • Insect-proof your stables using fine-mesh screens before the start of the fly season!
  • Use ceiling or wall mounted fans in stables to create a breeze – flies will find it harder to land on your horse, and a fan can also stimulate cool airflow to soothe itchy skin.
  • Keep horses in doors one hour before and after sunrise/sunset (this is when flies are most active) and consider stabling horses at night.
  • Moving horses farther than half a mile from stagnant water and ponds to reduce fly exposure – as this is where flies and mosquitoes breed! Also, take steps to improve pasture drainage to prevent fly breeding and clean the water trough regularly.
  • Apply natural insect repellents to the mane and tail region.


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