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Pine Ridge Equine Hospital

What Horse Owners Need to Know about Exercise Induced Pulmonary Hemorrhage (EIPH)

Brown horse with white socks in a rural field setting.

Could your horse be at risk for exercise-induced pulmonary hemorrhage (EIPH)? EIPH primarily affects Thoroughbred and Standardbred race horses but can also occur in any horse that spends time exercising intensely, according to a consensus statement published in the Journal of Veterinary Internal Medicine.

What Is EIPH?

EIPH causes hemorrhages (bleeding) in your horse's lungs when it gallops or participates in other strenuous activities. Intense activity creates pressure that strains your horse's lungs and cause breaks in blood vessels that supply blood to the lungs.

As the breaks heal, they scar over. The scarred area of the lung become less flexible, which means your horse has to work harder to breathe. Once EIPH develops, your horse is likely to experience more hemorrhages in the future. The more often hemorrhages happen, the greater the area of damage in the lungs.

What Causes EIPH?

A vacuum effect occurs every time your horse inhales. The negative pressure created by the effect helps oxygen travel from the nose to the lungs. Once air reaches the lungs, it passes through a thin membrane into small blood vessels in the lungs.

At the same time, pressure increases inside your horse's blood vessels, as the volume of red blood cells rises. The increase in red blood cells makes it easier for extra oxygen to reach every part of your horse's body during exercise. Pressure also rises as the horse's heart works harder.

As pressure builds up, the small blood vessels in the lungs begin to hemorrhage. Over time, the scar tissue caused by the hemorrhages can damage your horse's lungs.

Nose bleeds, frequent swallowing and coughing can be signs of EIPH. An otherwise healthy horse may take longer to recover from a long trail ride or struggle to be competitive during a race. Unfortunately EIPH tends to get worse as your horse get older. Horses can have EIPH even if they don't suffer bloody noses. Instead, the blood may collect in the windpipe where you can't see it.

If your horse has EIPH, you may notice that it chokes after exercise, or you might hear a whistling sound when your horse breathes.

What Can Be Done to Treat or Prevent EIPH?

Treatment options for EIPH include:

  • Salix (Furosemide).

This drug decreases stress on the small blood vessels in the lungs and reduces bleeding, according to The Horse. Although Salix can be helpful, many racetracks no longer allow it on race day due to concerns that it could enhance a horse's performance. USA Today reported that as of 2021, horses competing in the Triple Crown could no longer use the drug. Other races across the country have also banned Salix.

  • Nasal Dilators.

Nasal dilators work the same way as the breathing strips you use to reduce snoring or make it easier to breathe. A review of alternative therapeutic therapies that appeared in AAEP Proceedings noted that 40 to 50 percent of pulmonary (lung) resistance occurs in the nose. According to the review, nasal breathing strips keep the passages in the nose from collapsing and reduce pressure and airway resistance.

  • Concentrated Equine Serum.

Injections of concentrated equine serum may be helpful in reducing inflammation and decreasing mucus and the volume of red and white blood cells, according to the Proceedings review. Horses initially receive daily serum injections for five days, then receive weekly boosters.

Are you worried that your horse may have EIPH? Give us a call to arrange a visit with the equine veterinarian.


NCBI: Journal of Veterinary Internal Medicine: Exercise Induced Pulmonary Hemorrhage in Horses: American College of Veterinary Internal Medicine Consensus Statement, 5-6/2015

The Horse:EIPH: Exercise-Induced Pulmonary Hemorrhage

USA Today: Major Tracks to Ban Race-Day Use of Anti-Bleeding Medication, 4/18/2019

American Association of Equine Practitioners: Review of Alternative Therapies for EIPH