EIPH – Exercise-Induced Pulmonary Haemorrhage

When strenuous exercise causes bleeding within the lungs

Exercise-Induced Pulmonary Haemorrhage (EIPH) is bleeding that occurs within a horse's lungs during or following strenuous exercise.

You may also hear a horse with EIPH described as a “bleeder.”

That expression can be misleading. It does not necessarily mean that blood will be seen coming from the horse's nostrils. In many affected horses, the bleeding occurs deep within the lungs and may only be identified through veterinary examination.

EIPH is particularly well recognised in racehorses because of the very high cardiovascular and respiratory demands of racing, but it can occur in horses undertaking other forms of strenuous athletic exercise.

What actually happens in EIPH?

During intense exercise, a horse's heart and lungs have to work extraordinarily hard to supply oxygen to the exercising muscles.

Blood pressure within the tiny blood vessels surrounding the air sacs of the lungs can become extremely high. At the same time, large pressure changes occur within the airways as the horse breathes.

Under these extreme conditions, some of the microscopic blood vessels — called pulmonary capillaries — can rupture.

Small quantities of blood then leak into the airways and lung tissue.

This is the pulmonary haemorrhage part of Exercise-Induced Pulmonary Haemorrhage:

Pulmonary = relating to the lungs
Haemorrhage = bleeding

So, in everyday language:

EIPH means bleeding from very small blood vessels within the lungs associated with strenuous exercise.

The amount of bleeding can vary considerably between horses and between individual episodes of exercise.

Does a horse with EIPH bleed from its nose?

Usually, no.

This is one of the most important things to understand about EIPH.

The bleeding generally starts deep within the lungs. In many horses there is not enough blood travelling far enough up the airways to become visible externally.

When blood does appear at the nostrils, your vet may use the term epistaxis.

Epistaxis simply means bleeding from the nose.

Visible nasal bleeding following strenuous exercise can occur with EIPH, but it represents only a proportion of affected horses. Therefore:

No blood at the nostrils does not rule out EIPH.

Blood from a horse's nostrils can also have causes other than EIPH, so visible bleeding should always be investigated by a veterinary surgeon rather than assumed to be exercise-induced.

Why does EIPH happen?

There is unlikely to be one single cause.

During very strenuous exercise, several extraordinary physical changes occur simultaneously.

The horse's heart pumps enormous quantities of blood through the lungs, pressure within the pulmonary circulation rises substantially and powerful breathing movements create large changes in pressure within the chest and airways.

Together these forces can place considerable mechanical stress on the extremely delicate barrier separating blood within the pulmonary capillaries from air within the lungs.

If that barrier fails, blood can escape into the lung.

Repeated episodes may also contribute to inflammatory and structural changes within affected areas of lung tissue.

Which horses can be affected?

EIPH is most extensively recognised and studied in horses performing at very high exercise intensities, particularly:

• Thoroughbred racehorses
• Standardbred racehorses
• other horses undertaking repeated high-intensity athletic exercise

It should not, however, automatically be considered a racing-only problem.

The likelihood and significance of EIPH depend on the individual horse, the intensity of exercise and potentially several other physiological and environmental factors.

What might an owner or rider notice?

Many horses with EIPH show no obvious external sign at all.

Where signs are present, an owner, rider or trainer might notice:

• poorer performance than expected
• a horse appearing to tire sooner during intense work
• coughing following exercise
• unusual respiratory noise or increased respiratory effort
• taking longer than expected to recover after strenuous exercise
• reluctance or inability to maintain previous levels of performance
• occasionally, blood visible at one or both nostrils after exercise

These signs are not specific to EIPH.

Poor performance, coughing and abnormal recovery can have many different causes. EIPH is therefore something a veterinary surgeon may investigate rather than something that should be diagnosed from symptoms alone.

“My vet said the horse scoped as a bleeder” – what does that mean?

This is terminology owners involved with performance horses may commonly hear.

A vet may perform an endoscopic examination, often simply called “scoping.”

An endoscope is a flexible camera that allows the vet to examine the horse's upper airways and look towards the trachea — the windpipe leading towards the lungs.

Following strenuous exercise, blood originating from the lungs may become visible within the trachea.

Veterinary surgeons can grade the amount of blood they see. An owner may therefore hear expressions such as:

“There was blood on the scope.”
“The horse has EIPH.”
“The horse is a bleeder.”
“It was graded on the scope.”

These are different ways of describing evidence and severity of exercise-associated pulmonary bleeding.

The grade and its significance should be discussed with the examining veterinary surgeon in the context of that individual horse.

What is a BAL?

Another term an owner may encounter is BAL, meaning bronchoalveolar lavage.

It is sometimes described informally as a lung wash.

Fluid is introduced into a small area of the lower respiratory tract and then recovered so that the cells and other material within it can be examined.

Among other things, this can provide evidence of previous bleeding that might not be obvious during a routine examination.

For example, a laboratory may identify haemosiderin-containing macrophages.

That sounds complicated, but the principle is relatively simple.

Macrophages are cells that help clear material from tissues. Following bleeding within the lungs, they can take up iron-containing material left behind as red blood cells break down.

Finding these cells can therefore provide evidence that bleeding has occurred previously.

Why repeated EIPH matters

A single episode and repeated episodes are not necessarily the same thing.

When bleeding repeatedly occurs within lung tissue, the body has to clear the blood and repair the affected area.

Over time, repeated haemorrhage may be associated with inflammation and changes within parts of the lung.

For a performance horse, the important question is therefore not simply:

“Has this horse ever bled?”

but also:

“How frequently is it happening, how severe is it, and is it affecting the horse's respiratory health or performance?”

Those are veterinary questions requiring assessment of the individual horse.

When should I contact my vet?

Seek veterinary advice if a horse:

• has blood coming from one or both nostrils
• repeatedly coughs following exercise
• develops unexpected breathing difficulty
• suddenly performs substantially below its normal level
• takes unusually long to recover after exercise
• has previously been diagnosed with EIPH and its symptoms change or worsen

Significant respiratory distress or substantial unexplained bleeding should be treated as requiring prompt veterinary attention.

Do not assume that blood from the nostrils is EIPH simply because it occurs following exercise.

How is EIPH managed?

Management depends upon the individual horse, the severity and frequency of the bleeding, its intended athletic use and the rules governing medication within the relevant sport or competition.

Veterinary investigation may consider EIPH alongside other possible causes of respiratory difficulty or poor performance.

Depending upon the circumstances, your veterinary surgeon may discuss areas such as:

• exercise intensity and training
• respiratory health
• airway inflammation
• environmental dust and stable air quality
• recovery following strenuous exercise
• other conditions that could be contributing to poor performance
• appropriate veterinary treatment where indicated

Medication rules differ considerably between equestrian disciplines and jurisdictions.

Never use medication in an attempt to manage EIPH without veterinary guidance, particularly in a competition horse.

Supporting respiratory health

EIPH is a veterinary condition associated with the extreme pressures generated within the lungs during strenuous exercise.

Good respiratory management cannot guarantee that EIPH will be prevented, but maintaining a horse's overall respiratory health remains important, particularly for horses expected to perform athletically.

Useful everyday management includes:

• reducing unnecessary exposure to stable dust
• providing good ventilation
• using appropriate low-dust forage and bedding where required
• avoiding mouldy or dusty forage
• maintaining sensible conditioning and fitness programmes
• allowing appropriate recovery following demanding exercise
• investigating persistent coughing or reduced performance rather than simply working through it

A supplement should not be presented as treating, preventing or curing EIPH unless there is appropriate evidence and regulatory authority for such a claim.

The important thing to remember

EIPH is bleeding from tiny blood vessels within the lungs associated with strenuous exercise.

A horse does not have to show blood at its nostrils to be affected.

Some horses show few outward signs, while others may experience recurrent bleeding or reduced performance.

If EIPH is suspected, veterinary investigation is important because coughing, poor performance, slow recovery and nasal bleeding can have several different causes.

Understanding what is happening within the lungs is the first step towards making appropriate decisions for the individual horse.

Graphics for this page

Graphic 1 – Hero graphic

“EIPH – What Happens Inside the Horse's Lungs?”

Purpose: Immediate visual explanation of a condition that cannot normally be seen externally.

Show an athletic horse exercising, combined with a clear anatomical cutaway highlighting the lungs.

Include a magnified inset showing:

Normal pulmonary capillary → extreme exercise pressures → tiny blood vessel rupture → blood entering the airway

Minimal supporting wording:

Exercise-Induced Pulmonary Haemorrhage (EIPH)
Bleeding from tiny blood vessels within the lungs associated with strenuous exercise.

The graphic should specifically avoid showing dramatic blood pouring from the horse's nostrils because that would reinforce the misconception that all horses with EIPH visibly bleed.

Standalone footer:
JCG Supplements – Equine Health Hub
jcgsupplements.com
Owner education – not a substitute for veterinary diagnosis or treatment.

Graphic 2 – “A Bleeder Doesn't Necessarily Bleed From the Nose”

Create a simple progression:

Bleeding begins deep within the lungs

↓

Blood may enter the lower airways

↓

It may be detected when the horse is scoped

↓

Only some affected horses show blood at the nostrils

Include:

EIPH = Exercise-Induced Pulmonary Haemorrhage
Epistaxis = visible bleeding from the nose

Key message in prominent type:

No visible blood does not mean that EIPH has not occurred.

Standalone footer:
JCG Supplements – Equine Health Hub
jcgsupplements.com
Blood from the nostrils can have several causes. Seek veterinary advice.

Graphic 3 – “EIPH: Veterinary Words Explained”

A clean owner-reference graphic suitable for saving, sharing or printing.

EIPH
Exercise-Induced Pulmonary Haemorrhage
Bleeding within the lungs associated with strenuous exercise.

Bleeder
An informal term commonly used for a horse affected by EIPH.
It does not necessarily mean blood is visible externally.

Endoscopy / Scoping
A flexible camera examination that can allow a vet to look for blood within the airways after exercise.

Epistaxis
Blood visible from the nostril.

BAL / Bronchoalveolar Lavage
Sometimes called a “lung wash”; a veterinary procedure used to collect material from the lower respiratory tract for examination.

Haemosiderin-containing macrophages
Cells containing iron-rich material left after previous bleeding, which can provide evidence that bleeding has occurred.

Standalone footer:
JCG Supplements – Equine Health Hub
jcgsupplements.com
Clear explanations for horse owners. Veterinary terminology and investigation may vary according to the individual horse.

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People also asked

My horse coughs at the start of exercise. Should I be concerned?

An occasional cough at the start of exercise is not always a cause for alarm. Some horses may cough once or twice as they clear dust or mucus from their airways, particularly if they have been standing in the stable.

However, a horse that coughs regularly should not be ignored.

A persistent cough can be a sign of an underlying respiratory problem, including:

• Dust or irritation from hay, bedding or the stable environment.
• Mild airway inflammation.
• Equine asthma (formerly known as COPD or RAO in more severe cases).
• A viral or bacterial respiratory infection.
• Less commonly, other conditions affecting the lungs or upper airway.

You should pay particular attention if your horse also has:

• Nasal discharge.
• Increased breathing effort or flared nostrils.
• Reduced performance or tiring more quickly.
• Noisy breathing.
• A persistent cough at rest as well as during exercise.
• A raised temperature or signs of being unwell.

If the cough continues for more than a few days, becomes more frequent, affects your horse’s performance, or is accompanied by any other signs of illness, your veterinary surgeon should examine your horse. Early diagnosis can help identify the cause and allow appropriate treatment or management before the problem becomes more serious.

Many owners choose to include a respiratory supplement as part of their horse’s daily routine to help support healthy respiratory function, particularly during periods of increased workload, travel or environmental challenge. Used alongside good management practices, they can form a valuable part of a proactive approach to maintaining your horse’s respiratory wellbeing.

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