Treating Your Horse’s Summertime Allergies

Horse in a field of yellow flowers.


It is believed that over 50,000 horses in the UK suffer from summertime skin conditions. These have a number of causes, from feed hypersensitivity to nettle stings to allergies to the saliva in insect bites (sweet itch).

An allergy is a condition which causes the body to negatively react, either locally or systematically, to a certain substance, known as an allergen.

In horses, allergic reactions can be triggered by many things, from environmental allergens, such as dust, pollen and mould, to insect bites, substances in feeds and injections.

Localised reactions tend to appear as swelling and redness in the skin, which can sometimes cause itching, at the site of allergen contact, or hives across the whole body. The most severe reactions can affect additional parts of the anatomy, such as the respiratory and circulatory systems, which can be life-threatening if not immediately treated.


Avoidance and Prevention

The first line of defence should always be to remove the cause of the reaction and to avoid contact with the allergen in future.

One of the most common reactions is to insects, and those horses that are sensitive to bites are best helped through prevention.

If you have a horse that you know is bothered by insects, then liberal use of fly spray is a must, as is a full-body fly rug. It can also be helpful to stable your horse during the day, as the gnats that are most commonly responsible for causing reactions tend to be worst at dawn and dusk. For the worst affected horses and ponies, try placing a fan in the rafters of the stable to keep the air moving. This discourages gnats, which tend to be weak fliers.

Often antihistamines can be used alongside avoidance techniques in the treatment of seasonal allergies. It helps to start the horse on the antihistamines in late spring, before their reactions to insects, pollens etc. become too uncomfortable. In this scenario, the medication tends to be much more effective than it is once the problem has already begun, as once the reaction has started a corticosteroid is usually required to reverse the reaction and bring it under control.

The antihistamines sold for human consumption tend not to be very effective for equines, due to their sheer size, but an antihistamine drug known as hydroxyzine is usually highly effective.

For horses suffering from heaves, an allergic respiratory disease, avoiding the allergen is paramount. Horses should be kept outdoors rather than stabled, and rich pasture should be chosen over dusty paddocks. Alfalfa hay should be avoided, due to its level of mould dust, and substituted with grass hay instead. This should be dampened and soaked in water to eliminate dust particles, and fed from the ground. Uneaten hay should be removed daily.

Steroids and Supplements

The first goal should always be to work out what environmental factor is causing your horse’s allergy and how you can reduce contact with it. However, where the reaction is severe, the best course of action is to call your vet.

Most allergic reactions can be controlled using cortisone treatment. The sudden development of hives is quite common, and looks rather dramatic, but it can generally be reversed very quickly with a small yet aggressive dose of steroids to reduce the swelling. For those unwilling to submit their horse to medical intervention unless absolutely necessary, many vets will simply recommend bathing the horse with a mild shampoo, especially if the problem was caused by contact with an allergen.

If your horse has a history of severe allergic reactions due to season problems, such as fly bites, you should request a course of cortisone treatment from your vet, beginning around two weeks before the horse’s problems usually set in. This will mean that your horse can be managed with a lower dosage of dexamethasone throughout the season than if the allergy is allowed to manifest itself. The same is true for seasonal respiratory diseases like summer pasture heaves.

Some people also have success with non-prescription supplements such as ExTox from Equiform Nutrition. These will usually incorporate detox products, such as an antioxidant complexes, mycotoxin binders and nucleotides to support the horse’s immune system following exposure to mycotoxins, which are often found in cereal, grains, bedding and even grass, along with other problematic allergens.

Steroids, such as dexamethasone, might also be used in the case of heaves, along with bronchodilator drugs such as Ventipulmin to reduce inflammation and open up the airways. Although the most effective treatment for this condition is strict avoidance of aeroirritants, the causative particles which are inhaled, if avoidance is ineffective then the use of drugs is advocated. However, treatment for heaves is only ever temporary, and if the horse is kept in a dusty environment or fed dusty hay then it will always resurface.

Where anaphylactic shock has already occurred, this must be treated with the immediate administration of adrenalin such as epinephrine, and a steroid like dexamethasone to halt the inflammation and swelling and stop the horse from going into shock.

If your horse has allergies, don’t despair — most are manageable. However, it is absolutely paramount that you are willing to put the time into finding the cause of your horse’s discomfort and treating it appropriately.

A healthy horse is a happy horse, so make sure you keep your four-legged friend feeling comfortable this summer.

2 thoughts on “Treating Your Horse’s Summertime Allergies”

  1. Thank You for this info I have printed it , seems today I can think of anything else but the zeroing out of the Precious Mustangs in Wyoming……and I sit here here in Ohio , and cannot help them…….


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