Sweet itch or summer dermatitis is an allergic reaction of horses to the bites of midges. Midges are small, female Culicoides that feed on blood since they need a high protein meal to enable them to lay their eggs.
Although the disease has been known for centuries, the first scientific description of the link with midge bites was made in Australia in the 1950s by a vet called Riek.
Riek first noticed that the disease occurred only in areas where midges were abundant, then showed that when an extract of midges was injected into the skin of the affected horses, a small swelling appeared within a few minutes.
This type of "acute" reaction is typically seen in certain types of immune "hypersensitivity" or allergy and so Reik concluded that sweet itch was an allergy to midge bites.
Sweet itch is an equine skin condition which, although not serious, causes the horse intense irritation causing it to rub itself in any way possible leading to hair loss and thickening and inflammation of the skin usually in the mane, hindquarters and tail area.
The horse or pony's skin eventually becomes chronically thickened, wrinkled and blackened.
During the winter months, with no midges about, the sweet itch may disappear and the sore ares heal
Some horses are much more susceptible to sweet itch than others, and the condition can be hereditary.
A horse with sweet itch should be kept stabled on days when midges are more likely to be about, especially at dawn and dusk.
Fly repellents can help towards keeping away midges and gnats - but if you do turn your horse out put on a fly sheet or rug with a hood which covers him from head to toe and which covers the belly as well for extra protection.
Baby oil applied to the root of the mane and tail can stop the midges getting a grip to feed.
Treatment with corticosteroid creams, ointments or injections can help to reduce the inflammation in the skin.
Anti-histamines, such as benadryl, do not work as well as a treatment on horses as on humans and are best avoided.
Some horse owners have reported success treatment by adding garlic or cider vinegar to the horses feed. A horse that has been fed garlic gives off an odor that helps repel midges!