Why Does My Horse Cough? Causes and When to Worry

Name: Why Does My Horse Cough? Causes and When to Worry
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

Why does my horse cough? Most often, a cough means the airways are irritated by dust, hay, or ammonia in the barn, or by a chronic allergic condition called equine asthma. Sometimes it signals an infection, and occasionally it points to a physical blockage or airway problem that needs urgent care. Sorting out which one you are dealing with starts with the pattern of the cough and the other signs you see.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

A single cough after a dusty hay flake or a cold morning turnout is common and often harmless, but a cough that repeats every day for more than a couple of weeks is not normal and should be checked.
Equine asthma is the most common long-term cause of coughing in adult horses, and it is managed mainly by reducing dust and allergen exposure [1].
Horses cannot breathe through their mouths, so any nasal blockage or airway swelling affects them more than it would a dog or a person [2].
Fever, thick nasal discharge, swollen lymph nodes under the jaw, or a horse that is not eating point toward infection and need a same-day call.
Loud, honking breathing with a cough, or a horse that cannot swallow, is an emergency.

What a Cough Looks Like and What Is Normal

A cough is a reflex. The horse takes a quick deep breath, closes the airway briefly, then forces air out to clear something irritating the windpipe or lower airways.

Horses are obligate nasal breathers. They cannot breathe through their mouths at all, which is why their nasal passages are large and can expand during hard exercise to pull in more air [2]. That anatomy matters when you are trying to figure out where a problem is coming from. A cough that sounds wet and rattly usually comes from the lower airway. A cough that sounds harsh, honking, or noisy on inhalation often points higher up, in the larynx or throat.

So is it normal for horses to cough? An occasional cough is. A horse might cough once or twice when you first bring out dusty hay, when you ride on a windy day, or when you first start trotting after a long break. What is not normal is a cough that shows up every day, a cough that gets worse over weeks, or a cough paired with poor performance, nasal discharge, or a change in appetite or attitude.

Why Does My Horse Cough? The Main Causes

Dust, Hay, and Barn Air

This is the everyday cough most owners notice first. Dry hay, dusty bedding, indoor arenas, and ammonia from soiled stalls all send small particles into the air. The horse inhales them, the airways react, and out comes a cough. A dry cough that appears only in the barn or only when you first start work is a classic pattern. If the cough disappears on pasture turnout and comes back in the stall, the environment is the likely trigger.

Equine Asthma

Equine asthma is a chronic, noninfectious inflammatory disease of the lower airways in adult horses [1]. It used to be called heaves, broken wind, or COPD. The term now covers three related conditions: inflammatory airway disease, recurrent airway obstruction, and summer pasture recurrent airway obstruction [1]. Mild to moderate asthma matches the old inflammatory airway disease label, and severe asthma matches what was once called heaves [1].

All horses with asthma share airway inflammation, airway hyperresponsiveness, and airway remodeling [1]. In plain terms, the airways are inflamed, they overreact to irritants, and over time the tissue changes. Diagnosis is usually based on clinical signs plus a cytologic evaluation of bronchoalveolar lavage fluid, which is a fluid sample washed from deep in the lungs [1]. Reducing allergen exposure is the essential part of managing these horses, and medical treatment includes systemic or inhaled corticosteroids and bronchodilators [1].

If your horse has a dry cough that never quite goes away, asthma belongs on the list. So does a cough that comes with flared nostrils, a slight heave to the flank at rest, or a horse that seems to tire earlier than it used to.

Respiratory Infection

Bacterial and viral infections cause coughing too. Strangles, caused by Streptococcus equi subspecies equi, spreads when horses commingle at events, sales, or new stabling situations, and it can affect every horse on a farm [3]. In one report, a vaccinated horse that tested positive for S. equi and equine herpesvirus 4 developed a cough, an elevated body temperature, and nasal discharge 11 days after its first vaccination [3]. That timeline shows how a cough can be one part of a bigger infectious picture.

A study of tracheal lavage samples from horses with various respiratory signs grouped them by what owners and vets saw: some had no apparent symptoms, some had only coughing, some had only lymph node swelling, some had coughing plus lymph node swelling, and some had all three signs including nasal discharge [4]. That grouping is useful because it shows coughing alone can be its own category, and coughing with swollen glands or discharge is a different, more concerning one.

Choke and Airway Problems

Choke is a blockage of the esophagus, not the windpipe, but it can cause coughing, gagging, and food or saliva coming out of the nose. It is a veterinary emergency. Upper airway obstruction is another category. In a study of Colombian Criollo horses, 12 of 23 had upper airway obstruction, with recurrent laryngeal neuropathy the most common diagnosis at 83% and nasopharyngeal collapse next at 42% [5]. Affected horses had changes in how they moved air during exercise [5].

Exercise-induced pulmonary hemorrhage, or bleeding into the lungs during hard work, is another cause of coughing and poor performance. In a study of competitive draft pulling horses, 26% had exercise-induced pulmonary hemorrhage, 32% had recurrent laryngeal hemiplegia, and 82% had tracheal mucus [6]. Respiratory disease is common in horses and is often linked to poor performance in equine athletes [6].

Cause Comparison Table

Cause	Typical clues	How urgent
Dust or barn irritant	Dry cough only in the stall or when hay is opened, clears on pasture	Routine, improve air quality
Equine asthma	Daily cough, poor exercise tolerance, flared nostrils, heave line over time	Routine, but needs diagnosis and management [1]
Respiratory infection	Fever, nasal discharge, swollen lymph nodes, off feed, cough after commingling	Same day [3][4]
Choke	Gagging, food or saliva from the nose, distress, coughing while eating	Emergency now
Upper airway obstruction	Noisy or honking breathing, cough during exercise, poor performance	Same day to urgent [5]
Exercise-induced pulmonary hemorrhage	Cough and poor performance after hard work, sometimes blood at the nostrils	Same day [6]

Red Flags That Mean an Emergency

Call your veterinarian right away, or an emergency service if it is after hours, if you see any of these.

Your horse is struggling to breathe at rest, with flared nostrils and a visible effort in the flank.
Breathing is loud, honking, or noisy even when the horse is standing still.
Food, saliva, or green fluid is coming out of the nose, or the horse is gagging and stretching its neck (possible choke).
The horse will not eat or drink, or seems depressed and dull.
There is a high fever, or the horse is sweating for no clear reason.
Blood is visible at the nostrils after exercise.
The gums look pale, blue, or muddy.
The cough came on suddenly after a new horse arrived on the property, or after your horse returned from a show or sale.

Any of these can move fast in a horse. Do not wait to see if it improves overnight.

How to Help a Horse With a Cough at Home

While you wait for your vet, or while you work through a management plan, these steps are safe and often make a real difference.

Fix the Air

Soak hay or switch to a low-dust forage if your horse coughs when hay is put out.
Feed hay on the ground or well below the nose instead of high overhead, so dust and mold spores fall away from the airway.
Increase ventilation. Open doors and windows, and avoid closing a coughing horse into a tight, warm barn.
Strip and rebed stalls often. Ammonia from urine is a strong airway irritant.
Turn out as much as possible. Fresh air and movement help clear the airway.

Support the Horse

Keep light exercise going if your horse is comfortable. In a study of horses with severe asthma, a 25-minute standardized walk and trot session produced measurable bronchodilation, meaning the airways opened up after light field-applicable exercise [7]. That does not replace treatment, but gentle daily movement is reasonable for many coughing horses.
Offer fresh water at all times. A horse that is breathing hard loses fluid and can dry out its airway.
Do not give any medication, including human cough syrups or leftover antibiotics, without veterinary direction. Your veterinarian calculates any drug dose from your horse's weight and health status.

If you also have dogs at home and are comparing symptoms, our guides on Dog Coughing: When Should You Worry? and Why Is My Dog Coughing And Gagging And Wheezing explain how coughs differ across species. The rules are not the same, so do not transfer a dog treatment plan to your horse.

What Your Veterinarian Will Check and Test

Your vet will start with a full physical exam. That includes listening to the lungs and trachea with a stethoscope, checking the nostrils for discharge, feeling the lymph nodes under the jaw, taking a temperature, and watching the horse breathe at rest and after light exercise.

Depending on what they find, they may recommend:

A rebreathing exam, where a bag is held over the nose briefly to make the horse breathe deeper so lung sounds are easier to hear.
Endoscopy, passing a thin camera up the nose to look at the larynx, trachea, and where the airways branch. This is how upper airway obstruction and recurrent laryngeal neuropathy are identified [5].
A tracheal wash or bronchoalveolar lavage to collect airway fluid. Cytologic evaluation of bronchoalveolar lavage fluid is the standard way equine asthma is confirmed [1]. Tracheal lavage samples can also be cultured to look for beta-hemolytic streptococci and other bacteria [4].
Blood work, including a complete blood count and chemistry panel, to look for infection and inflammation.
Imaging such as radiographs or ultrasound if the vet suspects deeper lung disease.

Treatment depends entirely on the diagnosis. Asthma is managed with allergen reduction plus systemic or inhaled corticosteroids and bronchodilators [1]. Infections need targeted antimicrobials and supportive care. Choke needs the blockage relieved. Upper airway problems may need surgery or a change in training and management [5].

Prevention and Monitoring

The single most effective thing you can do for a horse with a chronic cough is control the air it breathes. That means low-dust forage, good ventilation, clean bedding, and as much turnout as your management allows. For horses with asthma, reducing allergen exposure is the essential part of long-term care [1].

Keep simple records. Note when the cough happens (at rest, during work, only in the stall), how many times a day, and whether anything else changed, such as appetite, energy, or nasal discharge. A short log helps your vet see patterns that a single exam might miss.

Watch performance closely. Respiratory disease is common in horses and is often tied to poor performance in equine athletes [6]. A horse that used to breeze through a workout and now coughs and fades is telling you something. In draft pulling horses, tracheal mucus was found in 82% of the study population, which shows how often airway irritation shows up in hard-working horses [6].

If your horse commingles with others at shows, sales, or a new barn, keep an eye out for cough, fever, and nasal discharge in the two weeks after arrival. Strangles spreads through commingling and can affect an entire farm [3].

Limitations and When to Contact a Veterinarian

This article gives general guidance only. Every horse is an individual, and a cough that looks mild in one horse can be the first sign of something serious in another. Only your veterinarian can examine your horse, run the right tests, and prescribe treatment.

Contact a veterinarian the same day if your horse has a fever, thick or colored nasal discharge, swollen lymph nodes under the jaw, a reduced appetite, or a cough that has lasted more than a few days or is getting worse. Call immediately, day or night, if your horse is struggling to breathe at rest, making loud or honking noises with each breath, gagging with food or fluid coming from the nose, or showing blood at the nostrils after exercise.

For a horse with a long-standing dry cough and no other signs, a routine visit is reasonable, but do not put it off for months. Chronic airway inflammation tends to worsen without management [1].

Frequently Asked Questions

Is it normal for my horse to cough every day?

No. An occasional cough around dusty hay or on a cold morning can be normal, but a daily cough is a sign of ongoing airway irritation or disease. Horses with equine asthma often cough every day, and that pattern deserves a veterinary exam [1].

Why does my horse have a dry cough?

A dry cough usually points to irritation or inflammation in the lower airway instead of infection with mucus production. Dust, mold spores, ammonia, and equine asthma are the most common reasons. If the cough is dry and appears mainly in the barn, start by improving ventilation and reducing dust while you arrange a vet visit.

How can I help my horse with a cough before the vet comes?

Improve the air first. Soak or switch hay, increase ventilation, strip wet bedding, and turn the horse out as much as possible. Light walking or trotting is reasonable if the horse is comfortable, since gentle exercise can open the airways in horses with severe asthma [7]. Do not give any medication without veterinary direction.

Can a cough mean my horse has an infection?

Yes. Coughing is one of the signs seen with respiratory infections, including strangles, which spreads when horses commingle at events, sales, or new stabling situations [3]. A study of horses with respiratory signs found that some had coughing alone, while others had coughing plus swollen lymph nodes or nasal discharge [4]. Fever and swollen glands make infection more likely.

When should I call the vet for a horse cough?

Call the same day if there is fever, nasal discharge, swollen lymph nodes, loss of appetite, or a cough that is getting worse. Call immediately if your horse is struggling to breathe at rest, making loud or honking sounds, gagging with fluid from the nose, or showing blood at the nostrils after work. A dry cough with no other signs can wait for a routine visit, but it should not wait for months.

References

Asthma in Horses - Respiratory System. Merck Veterinary Manual.
Introduction to Lung and Airway Disorders of Horses - Horse Owners. Merck Veterinary Manual.
Closing the Stable Door on Strangles: Serological Responses of Vaccinated Horses on a Farm Following the Arrival of a New Horse. Animals : an open access journal from MDPI, 2025.
Analysis of the presence of Beta-hemolytic streptococci and cytological profiles in horse tracheal lavage samples with diverse clinical respiratory symptoms. BMC veterinary research, 2025.
The effects of upper airway obstruction on oxygen consumption and ventilatory variables in Colombian criollo horses. Journal of veterinary internal medicine, 2026.
Prevalence of Exercise-Induced Pulmonary Hemorrhage, Tracheal Mucus and Recurrent Laryngeal Neuropathy in Competitive Draft Pulling Horses. Journal of equine veterinary science, 2023.
Field-applicable low-intensity exercise induces bronchodilation in horses with severe asthma. Equine veterinary journal, 2026.