Horse Sweet Itch: Welfare and Management of Insect Hypersensitivity

Sweet itch (culicoides hypersensitivity) causes intense, chronic itching in affected horses and requires active management to prevent self-injury and maintain welfare.

Key Facts

Sweet itch is caused by an allergic reaction to Culicoides biting midge saliva
Affected horses experience extreme pruritus (itching) that leads to rubbing, self-injury, and hair loss
The mane, tail, withers, and belly are most commonly affected
Certain breeds including Icelandic horses (when moved to midge-endemic areas) and native ponies are particularly susceptible
Prevention relies on reducing midge exposure through fine-mesh rugs, stabling during peak midge activity, and repellents
No permanent cure exists, but allergy-specific immunotherapy can reduce sensitivity in some horses

Welfare Considerations

Sweet itch causes genuine suffering through constant, overwhelming itching that affected horses attempt to relieve through sometimes violent rubbing. Horses have been observed rubbing against fences until skin is broken and bleeding, and the sleep deprivation caused by nocturnal itching significantly impacts overall welfare and temperament. The chronic nature of the condition — worsening each summer over a horse's lifetime — means welfare management must be consistently maintained year after year. Horses with severe, uncontrolled sweet itch have significantly reduced quality of life.

What You Can Do

Fit affected horses with full-body sweet itch rugs with face and belly coverage from April through October
Stable horses at dawn and dusk when Culicoides midges are most active
Apply veterinary-recommended insect repellents, reapplied regularly according to instructions
Move horses away from standing water and damp, sheltered areas where midges breed
Discuss antihistamine or corticosteroid treatment with your vet for severe episodes
Consider immunotherapy referral to a veterinary dermatologist for horses with severe, poorly controlled symptoms