sweet itch

Sweet itch can affect any horse and there’s currently no cure. What can you do to give your equine friend some relief?

Yesterday afternoon I was in the stable when another boarder called me over to take a look at her horse’s tail. He had begun to rub the top of it raw, much to his rider’s distress – this horse has a long, thick, luxurious tail that is a source of great pride to her. The idea that her horse might have sweet itch practically sent her into a full blown panic attack. And that may not be an overreaction given how badly this condition can plague a horse, especially as there is presently no cure for it.

An Itch By Any Other Name…

Sweet itch has many different names, including summer itch and Culicoides hypersensitivity. It is caused by an overreaction of the horse’s immune system (an allergic response) to the harmless proteins in midge saliva when these insects bite the horse. It results in a localized reaction at the bite site. The midges are especially drawn to horses with a depressed immune system. Stress, toxins, poor nutrition and more can affect the acid mantle of a horse’s skin. This layer protects the horse from midges as well as parasites and bacteria, and once damaged, it leaves the horse open to developing hypersensitivities.

The condition otherwise has no favorite victims – it affects horses, ponies and donkeys all over the world. You will most commonly see sweet itch begin between the ages of one and five, although there is some evidence that a stressed immune system can tip the horse into reactivity at any age. There may also be hereditary and environmental factors that predispose the horse to the condition. Luckily, it is not contagious.

Know Thy Enemy

The offending midges are tiny, with a wing length of approximately 1.4mm. They like to breed in moist soil or vegetation, and cannot fly more than few hundred yards from where they originate. They favor calm, twilit conditions, and will not fly in heavy rain, clear sunshine, and windy or drought conditions.

The females are the offenders. While the males feed on nectar, the females seek out a blood meal to mature their eggs. Dorsal feeders are the most common, and will bite the horse around the ears, poll, mane and tail head. Ventral feeders are less common, and will feed around the horse’s face, chest and belly.

Because sweet itch is caused by midges, it is at its worst during the life cycle of the insects – mainly the spring and summer months. The severity of the horse’s reaction can vary from season to season, depending on the number of midges – and that is linked to whether the weather conditions that year are favorable for breeding.

Signs and Symptoms

Diagnosis is fairly simple, and signs/symptoms include:

• Lesions • Broken hairs
• Bald patches
• Bleeding and/or exudative dermatitis (weeping sores)
• Potential secondary infections, which can require antibiotics
• Affected skin can become thicker and wrinkled, with fewer, coarser hairs
• Flaky dandruff

Horses will be intensely itchy and will often swish their tails aggressively, stomp their feet, roll, pace the field, seek mutual grooming, develop head shaking and scratch themselves excessively on whatever they can find, resulting in self-trauma. Many riders report understandable personality changes in their horses during the worst periods. These include irritability, impatience and a short attention span for work. Overall, this can make riding difficult and unpleasant for both horse and rider.

Prevention and Relief

There is currently no cure for sweet itch, so helping your horse get some relief revolves around three main points: reducing your horse’s exposure to midges, managing the pests that do get to your horse, and reducing the resulting itchiness. Once your horse has been bitten, irritation begins, so prevention is key. Start developing a plan well before midge season starts.

1. Reduce your horse’s exposure

• Midges cannot travel far from their breeding ground, so managing your horse’s environment is key. If possible, keep your horse away from boggy areas where midges like to live and breed. Be vigilant about dumping standing water in containers around the barn, keep water troughs clean and fresh and pastures well drained.
• Keep your horse inside during times of the day when midges are at their worst – one hour before and after both sunrise and sunset, or even overnight. You can install fans to keep a breeze moving through the barn, which will make it less pleasant for the midges to hang around your stable. You can also install fine screens over the doors and windows. Note that in severe cases, some horses will be so itchy that they may use their downtime in the stall to do even more damage to themselves.

2. Managing the pests that do get to your horse

A full coverage blanket or sheet specially designed for horses with sweet itch is likely your best bet to help prevent midges from biting the parts of your horse they find most tasty.
• Insecticides and repellants can be used, but for good, long-lasting coverage, heavy chemicals are recommended, such as DEET, permethrin and benzyl benzoate. However, when such products are needed and used daily, they can eventually have the opposite intended effect by damaging the horse’s immune system. There are natural fly repellants out there, and some people have reported success with a dilution of Avon’s Skin So Soft.
• You can try coating smaller affected areas of your horse with something midges do not like to land on – products formulated for this purpose are usually an oil or grease substance. They can be effective but messy.
• Manage your horse’s diet for a better immune system. Do not give him sugary feeds or treats. You can supplement with fatty acids, such as flax seed and fish oil. Vitamin C and/or blue green algae are great for boosting immunity, and garlic or apple cider vinegar can help make your horse less palatable to midges. Helpful herbs may include chamomile, calendula, meadowsweet, Echinacea, rosehips and dandelion. Talk to a holistic veterinarian about developing a program for your horse.
• BioEos Ltd. has developed a promising immunotherapy program for horses based on a new sweet itch capsule.

3. Nix the itch

• Antihistamines can offer some relief for some horses.
• Corticosteroids may be used in severe cases but they can have side effects, only offer temporary relief, and require higher doses over time.
• Topical creams, lotions or sprays can offer some relief to irritated areas. They may include steroid creams, Calamine, or products that include chamomile, calendula, chickweed and/or aloe vera. • The homeopathic Apis can assist with acute swelling, itching and pain.

A diagnosis of sweet itch can be difficult to adjust to at first – it isn’t easy to watch your equine friend struggling with so much discomfort. And it can make riding and other activities frustrating if your horse becomes irritable and fussy. But if you follow the above suggestions, there is some relief in sight!

Isabella Edwards is an equine enthusiast and avid competitor living in Ontario, Canada. She and her mare compete at the provincial level in both dressage and hunter/jumper.