How to Treat a Horse with Severe Respiratory Allergies

by on March 7th, 2015
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Respiratory allergies are the second most common reason why horses have to drop out of competition, behind only musculoskeletal problems such as leg injuries. Allergies to dust, molds and fungal spores are the main causes of symptoms. Treatment varies on just how badly the horse has been affected. If the horse has been bleeding in the lungs, then the horse may need to be put down.

Causes and Symptoms

There is some controversy as to how horses develop respiratory allergies. Horses that are the same breed that receive the same feed, stabling and exercise conditions may or may not develop allergies. Just why some horses develop allergies would go a long way to helping how to treat a horse with severe respiratory allergies.

According to N. Edward Robinson, BVet Med, PhD, MRCVS, over 50% of horses will develop respiratory allergies when the horse is six or older. Allergens such as dust, dust mites, molds, pollens or small particles in straw or hay trigger symptoms. Symptoms include a constant snorting or coughing, especially when eating hay, which progresses to wheezing. Horses may or may not expel or drip mucus.

Eventually, this wheezing also occurs during exercise. This is commonly called “heaves” as the cough does sound similar to the word “heave.” The horse often develops a “heave line” around the rib cage. This line becomes dark when the horse coughs. Affected horses often loose weight, lose condition and cannot exercise or compete in horse sports as well as before.


Medication used depends on what type of allergic respiratory disease the horse has developed. Inflammatory airway disease needs a combination of antibiotics, bronchodilators and drugs to dry up mucus production. Horses with either chronic obstructive pulmonary disease (COPD) or recurrent airway obstruction (RAO) can be treated with bronchodilators and, if the vet warrants, anti-inflammatory steroids. The latter is especially helpful for sudden flare-ups, according to Jean Hofve, DVM.

But medication is often not helpful for horses that have been affected so badly that their lungs are bleeding. Blood often drips or flows from one or both nostrils. It cannot be positively diagnosed until the horse is checked out with an endoscope. These horses may have to be put down if an owner is unwilling to keep a horse that cannot compete in sporting events.

Environment Changes

Keeping horses in dusty stalls can trigger attacks. Whenever possible, these horses need to be kept outside and exercised outside. Good quality hay is not very dusty, although watering the hay down will cut down on dust. Horses suffering from inflammatory airway disease often respond very well to environment changes and may not need long bouts of medication, according to The Complete Equine Veterinary Manual (David & Charles; 2004.)

Storing hay or straw in a separate building away from affected horses can also cut down on the amount of allergens that triggers coughing and heaving. Horses need to be kept outside while stalls are being cleaned because this is when dust is flung about. Feeding rolled grains should be avoided as this is dusty. Soiled bedding needs to be removed at least twice a day as mold from waste or urine may trigger the horse’s symptoms.


Horses with respiratory allergies may have diseases caused by allergens. Horses can still live if their lungs have bled, however their sporting careers would be finished. It may also be questionable to breed such horses. If an owner is willing to learn how to treat a horse with severe respiratory allergies and takes the time to make the lifestyle adjustments, the horse can still live out its life as a companion.


Pavord, Marcy and Tony Pavord, BVSc, MRCVS. The Complete Equine Veterinary Manual. .

Sellnow, Les. “Respiratory Allergies.” The Horse. September, 2000.

Hofve, Jean, DVM. “Respiratory Conditions in Horses.”

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