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Every time your horse coughs, it means something

No cough is normal. If your horse is coughing during warm-up, while exercising, or while at rest in the barn, it should always be considered abnormal. There are many reasons your horse may be coughing—from mild allergies to equine asthma or even an infection—and a cough should always be brought to the attention of your veterinarian.

Heaves, COPD, and IAD are all names for equine asthma

Equine asthma is a spectrum disorder, meaning that “equine asthma syndrome” is an umbrella term used to group together all the long-term, inflammatory diseases that affect a horse’s lungs that aren’t caused by an infection and are not contagious.

Equine asthma ranges from mild to moderate (formerly known as inflammatory airway disease, or IAD) to severe (previously known as heaves; recurrent airway obstruction, or RAO; and chronic obstructive pulmonary disease, or COPD). Summer pasture-associated recurrent airway obstruction (SPARAO or SPAOPD) also falls under the equine asthma umbrella.

What triggers asthma in horses?

In a word: dust. The feed, the bedding, the stabling, the cleaning, and the sweeping—the very care you provide is often a source of dust particles and endotoxins, so small that you can’t see them.

Dust particles that are small enough to be inhaled are called “respirable particles” and can cause inflammation deep in the lungs of susceptible horses, making it difficult for them to breathe. The amount of dust in the air as well as the size and source of the dust are all risk factors for triggering equine asthma symptoms.

The use of hay nets is associated with 4x as much exposure to respirable particles as feeding the same hay from the ground.
Even good-quality hay can have 10x the dust concentration of pelleted hay.
The environment can also play a key role in the triggering and development of equine asthma. Learn more about how managing your horse’s environment can help control their symptoms and maintain their long-term respiratory health.

Learn how to modify your horse’s environment to reduce dust

Learn now

How do I know if my horse has asthma?

At rest, a healthy horse takes 10 to 14 breaths per minute, inhaling 60 litres of air or more in that time. A horse performing a moderately strenuous exercise takes 150 or more breaths per minute, inhaling over 2250 litres of air with less than a second for each breath.

But a horse diagnosed with equine asthma, whose lung function is restricted by inflammation, may be reluctant to exercise and may cough, wheeze, or even struggle to breathe.

It’s estimated that 17% of horses have severe equine asthma, while another 68%-77% of pleasure horses are affected by mild to moderate asthma. Such a high prevalence of asthma in horses means that many people think it is normal for a horse to cough, especially at the beginning of a ride or in a dusty barn. But no cough is normal, and the most common cause of a cough in horses is equine asthma.

A diagnosis depends on a full exam by your veterinarian, but signs and symptoms to watch for include:


  • Occasional

  • Slight nasal

  • Poor

  • Reduced willingness
    to exercise


  • Frequent cough

  • Difficulty breathing
    even at rest

  • Exercise

  • Flared nostrils

  • Wheezing or

  • Lethargy

  • Shortness of
    breath and/or fast

  • Reduced appetite/
    weight loss

Why it’s important to treat equine asthma

When a horse is suffering from severe equine asthma, it’s easy to see how their quality of life is being affected by their condition because every breath is difficult. But it’s important to understand that horses living with mild to moderate asthma are also being affected, and it’s more than a simple cough or runny nose.

Horses with inflammation in their lungs struggle to expel enough air, which eventually leads to uneven ventilation: parts of their lungs get enough oxygen, but other parts do not. This leads to low blood oxygen levels during exercise, which affects athletic function and performance.

There is also evidence that, if left untreated, mild to moderate equine asthma can develop into a more severe form of the disease. In severe asthma, horses may struggle to walk from the barn to the paddock, and they may develop “heave lines” where their oblique abdominal muscles become hypertrophied (or exaggerated) from the effort required to push air out of their lungs.

Horses living with untreated severe equine asthma may also become quite thin due to the high number of calories they use just to breathe and their difficulty eating.

Diagnosing equine asthma

Veterinarian examining horse with image of stomach

After observing your horse and talking to your vet about the symptoms you have observed, your veterinarian will need to perform a thorough physical examination of your horse. A diagnosis of equine asthma may also require your veterinarian to perform additional tests:

Airway endoscopy: This test allows your veterinarian to look down your horse’s windpipe and into the lungs. They will introduce a narrow tube with a camera on the end into your horse’s nostril and thread it through the airway, allowing them to see what may be causing your horse’s symptoms.

“Lung wash” (also called a bronchoalveolar lavage): This test involves introducing a small amount of sterile saline into your horse’s lungs and then sucking it back out. The analysis of the fluid collected during this procedure can help to diagnose equine asthma or other potential lung infections.

Equine asthma treatment plan

Although equine asthma is a chronic condition that cannot be fully cured, it can be managed. Environmental modification, including possible changes to the horse’s feeding regimen, and medication work together to decrease the inflammation deep within the horse’s lungs and make breathing easier.