Equine Sweet Itch Welfare: Insect Hypersensitivity and Management

Sweet itch (insect bite hypersensitivity, IBH) is the most common allergic skin condition in horses, caused by hypersensitivity to Culicoides midge saliva. Affected horses experience intense, chronic pruritus that severely impairs quality of life during the summer months.

Key Facts

Up to 5% of horses in the UK show clinical signs of sweet itch, with higher prevalence in certain breeds
Icelandic, Exmoor, and Welsh ponies show disproportionately high prevalence
Clinical signs typically begin in spring and peak in summer, coinciding with Culicoides activity
Chronic scratching leads to hair loss, skin thickening, weeping lesions, and secondary bacterial infection
The condition is lifelong — affected horses require management throughout their lives

Welfare Considerations

Sweet itch causes intense, persistent pruritus that prevents affected horses from resting normally, eating without distraction, and engaging in natural behaviour. Chronic cases develop thickened, traumatised skin that is painful as well as itchy. Secondary bacterial infections cause additional suffering. Management revolves around preventing midge bites using full-body fly rugs from dawn to dusk, stable housing during peak midge activity periods, application of repellents containing DEET, and fan systems to reduce midge access. Medical treatments including cytopoint injections and immunotherapy are being developed. Welfare assessment should evaluate both the allergic response and the restriction imposed by management strategies.

What You Can Do

Fit a full-coverage sweet itch rug from late March to October for affected horses
Stable affected horses during peak midge activity periods (dawn and dusk)
Apply DEET-based insect repellent to exposed areas such as ears and belly
Consult a veterinary dermatologist about immunotherapy options for severe cases
Support research into sweet itch immunotherapy and genetic susceptibility