Equine Sweet Itch: Managing Insect Hypersensitivity in Horses

Sweet itch is an intensely pruritic allergic skin condition in horses caused by hypersensitivity to Culicoides midge bites. Without management, affected horses suffer severe, year-round distress.

Key Facts

Sweet itch (insect bite hypersensitivity, IBH) affects 2-5% of horses in temperate regions where Culicoides midges are present
Affected horses develop intense pruritus, hair loss, skin thickening, and self-trauma through rubbing
The condition is heritable — certain breeds including Icelandic horses and Welsh ponies have higher prevalence
Culicoides midges are most active at dawn and dusk — housing horses during these periods significantly reduces exposure
No cure exists; management focuses on reducing midge exposure through barriers, rugs, and insect repellents

Welfare Considerations

Sweet itch causes severe, year-round suffering in affected horses. The constant itch drives horses to rub against any available surface, causing hair loss, open wounds, and secondary infections that compound the primary allergic response. Without management, affected horses experience disrupted sleep, weight loss from energy spent managing discomfort, and significant psychological distress. Effective management requires a combination of approaches: specialist sweet itch rugs providing full body coverage, housing during peak midge activity, application of insect repellents, and in severe cases, allergen-specific immunotherapy. Early diagnosis and consistent preventive management are essential to minimising welfare impact.

What You Can Do

If your horse has unexplained seasonal pruritus, consult a vet experienced in equine dermatology
Invest in a well-fitting sweet itch rug and maintain it through midge season to reduce exposure
House horses during dawn and dusk when Culicoides midges are most active
Consider allergen-specific immunotherapy for severely affected horses after specialist diagnosis