What Is Sweet Itch?
Sweet itch is an allergic skin reaction to proteins in the saliva of Culicoides midges. It is caused by the bites of many types of flies and mosquitoes.
Clinical signs vary from papules (skin lumps) and persistent itching to self-trauma (rubbing on objects, biting themselves) including hair loss, wounds and skin thickening. If left untreated, secondary bacterial infections can aggravate the skin lesions.
Depending on the insect involved, the distribution of skin lesions varies from mane, tail, belly to face, ears, neck.
How Is Sweet Itch Diagnosed?
The diagnosis is often based on history, clinical signs and elimination of other potential causes for itching and hair loss. Many allergies can present the same skin lesions, therefore intradermal skin testing has been used to confirm what type of allergens have caused the reaction.
Preventing Sweet Itch
As it is caused by an immune response of the body (in order to defend itself from foreign substances), reducing a horse’s exposure to biting insects is the most important factor.
Follow the next steps in order to protect your horse from insect bites:
- Keep the horse stabled at times of day when midges are active (usually around dawn and dusk)
- Use a fly rug and fly mask when the horse is turned out. Make sure the rug is covering all the susceptible body areas
- Avoid turnout near stagnant or moving water, trees and woods
- Clean water buckets regularly
- Place insect netting over stable doors/ windows
- Use a fan within the stables
- Apply long-lasting insect repellents (sprays, creams) especially in the early morning and evening. Pyrethroid or cypermethrin containing products are often the most effective.
- Natural food supplements containing nicotinamide (product Cavalesse) can support the immune system and protect the skin
As mentioned before, minimal exposure to insects is the best cure for this disease. Pharmacological treatment is often symptomatic:
- Hypoallergenic shampoos can reduce itching and moisturise dry skin
- Anti-bacterial non-irritating shampoos (including shampoos containing chlorohexidine) can reduce secondary bacterial infections
- Cold water can reduce inflammation and severity of itching
- Use of antibiotic cream can prevent secondary bacterial infections
- Use of corticosteroid containing cream can reduce severity of itching and inflammation
- Dietary supplementation with omega fatty acids can reduce skin inflammation
- Anti-histamines can be used to relieve itching but their use has been proved to be often ineffective
- Corticosteroids have been successfully used in the management of allergies but their association with adverse effects (laminitis, immunosuppression) makes them unsuitable for a long-term therapy
- Allergen specific immunotherapy (vaccine) is currently being tested and might become the most effective long-term management in the future
Please note: Sweet itch is a major welfare concern. It can cause massive distress and discomfort for horses. Therefore, if the disease is not under control, please contact your vet.