Exercise Induced Pulmonary Hemorrhage in Horses

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Key takeaways

Exercise-Induced Pulmonary Hemorrhage (EIPH) is a condition in which the horse bleeds from the small vessels in the lungs into the airways as a result of strenuous exercise.

  • In severe cases, there is sufficient blood loss to cause a nosebleed, but in most cases there are no symptoms or only signs of poor performance
  • Veterinary attention helps determine the grade of EIPH and begin treatment to prevent scar tissue from forming in the lungs
  • Diagnostic tools include physical examination, endoscopy, and bronchoalveolar lavage
  • Treatment and prevention involves diuretics, although these are banned on the day of competition in certain regions
  • EIPH is not generally life-threatening, although it may shorten a competitive horse’s career
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A closer look: Exercise Induced Pulmonary Hemorrhage in Horses

Exercise Induced Pulmonary Hemorrhage (EIPH) is a common condition in horses that compete at high speeds or with high levels of exertion, including:

  • Racers
  • Polo ponies
  • 3-day event horses
  • Barrel racers
  • Show jumpers

All breeds of horse used for sport are at risk.

Horses showing symptoms of EIPH require prompt veterinary examination. Although EIPH is not life-threatening, severe cases can result in scarring of the lungs that can impact performance. Prompt examination allows for treatment to begin to reduce the severity of episodes.

Risk factors

A grade system has been devised for EIPH to help veterinarians and owners understand the severity of EIPH. Even in the most severe grade, it is possible for the horse to show no symptoms. Grading is only possible with veterinary examination after strenuous exercise.

Most low grade EIPH cases show no symptoms. Therefore, horses are typically diagnosed with EIPH at higher grades, usually after developing a nosebleed during or after exercise. Some horses may be diagnosed during veterinary examination for poor performance.

Possible causes

The barrier between the air and the blood in the lungs of horses is very thin, so that oxygen can be transferred to the blood quickly and efficiently. When the air pressure is normal, such as when the horse is at rest, this barrier is strong enough to keep the blood inside the vessels. When the air pressure increases, such as when the horse is exercising, the barrier cannot withstand the force and it ruptures, allowing blood to enter into the lungs. That blood travels up with the exhaled air from the lungs to the trachea. If sufficient blood is present, it comes out of the nostrils of the horse.

Main symptoms

Most cases of EIPH show no symptoms, however some may show signs of poor performance. With more severe cases, horses develop a nosebleed during or after exercise.

Testing and diagnosis

Diagnosis of EIPH primarily focuses on identifying the source of bleeding in horses that have nosebleeds. Diagnostic tools include:

  • Physical examination
  • Post-exercise endoscopic examination (feeding a camera into the trachea to check for blood)
  • Bronchoalveolar lavage (flushing water into the trachea and examining the material that it picks up)
  • Ultrasound or X-rays of the chest

Steps to Recovery

Treatment for EIPH is a diuretic that draws water out of the blood, lowering the overall blood pressure. Usually this is administered just before the horse performs, such as before races. Nasal strips that open the nostrils wider than usual are also used to increase airflow during exercise, and may improve performance.

In severe cases, horses may need a reduction in the intensity of exercise, such as changing to an alternative career or retirement.

EIPH is not curable. Horses that continue to engage in heavy exercise continue to bleed from their lungs. EIPH shortens the careers of some horses, and often results in poor performance. With continued episodes of EIPH, horses may develop scarring in their lungs that reduces their lung function. Horses that stop participating in strenuous activity stop experiencing EIPH.


Administering a diuretic to the horse prior to strenuous exercise can help prevent EIPH or reduce the severity of episodes. In some cases, where it is allowed by the competition’s governing bodies, diuretics can be administered on race or performance day as well.

EIPH is not contagious.

Is Exercise Induced Pulmonary Hemorrhage in Horses common?

EIPH is common in horses that participate in sport.

Typical Treatment

  • Diuretics


Kara M. Lascola , DVM, MS, DACVIM - Writing for Merck Veterinary Manual
"Frederik J. Derksen DVM PhD DACVIM Kurt J. Williams DVM PhD DACVP Alice Stack MVB" - Writing for Compendium: Continuing Education for Veterinarians
Kelly Hebner, BSc (Kin), MSc - Writing for Mad Bard
Erica Larson - Writing for The Horse
Stacey Oke, DVM, MSc - Writing for The Horse
Alexandra Beckstett, The Horse Managing Editor - Writing for The Horse

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