Sweet itch in horses: what is it and how can it be controlled?

The affliction is mainly seen in pastured horses, especially those that sleep out at night and are exposed to midges, writes Dr Mac.

- 

Sweet itch in horses is defined as an allergic reaction to the bites of tiny flying midges (Culicoides spp.) The term was originally invented to describe crusty lesions around the manes and tails of working horses (as well as donkeys and mules) in the British Isles.

Sweet itch is also sometimes used to describe the hairless patches seen on the faces of horses in South Africa, but these symptoms can also be caused by biting flies (Stomoxys calcitrans) or tick larvae attaching under the jaws and in the manes and ears of grazing horses. The itching makes horses rub their hair off.

Although all the horses on a farm are bitten by Culicoides midges at the same time, not all of them will show signs of sweet itch. Severe swelling and crusts seen in affected horses are possibly due to allergic reactions and often occur in horses with similar bloodlines.