Last Updated on March 15, 2022 by Allison Price

Horses can suffer silent injuries such as exercise-induced pulmonary hemorhage (EIPH) which is also known to horses. It occurs deep in the lungs and trainers and riders may not be able to detect it. Horses can develop EIPH when their pulmonary blood vessels rupture. Endoscopic examination can detect lung bleeding. Endoscopic examination uses a thin tube with a camera attached that is passed through horses to examine the upper airway. Lung washes or bronchoalveolar lvage (“BAL”) can be used to detect lung bleeding. Horses can develop lung irritation from blood in their lungs and lower airways.

Numerous studies have shown that most horses who exercise experience EIPH during intense exercise. Only 5% show blood around the nostrils.


FLAIR(r), Strips have been shown to decrease resistance to breathing, which places less stress on the blood vessels. This results in fewer ruptured blood vessels within the lungs. FLAIR Strips can be used in intense exercise, training or competition. This reduces the risk of lung damage and promotes optimal respiratory health.


Many low- and intermediate-level horse bleeders will not show visible signs of lung bleeding. However, symptoms you may notice include:

  • Poor Performance
  • Coughing
  • Extended cooling-out
  • Frequent Swallowing

Horses can cause more damage:

  • Gallops Fast and Often
  • Use Extreme Foots on very hard and soft surfaces
  • Carry More Weight (the heavier the bleeding, the more you are likely to carry).

EIPH can cause scar tissue to form in the lungs, and possibly future bleeding episodes. Repeated episodes of EIPH can cause lung damage that could reduce a horse’s ability to compete.


Horses don’t need to gallop to bleed. Japan’s research shows that horses canter at speeds up to 20 mph, which is a very slow speed for a racehorse. This was due to damage to their lungs from broken blood vessels. Lung bleeding can occur in horses even when they are doing light exercise like trotting on a treadmill.

Some blood vessels in the lungs are damaged when a horse canter more than a slow trot. Although the initial damage to the lung is limited to the top of the lung, it can spread over time with galloping, cantering and racing. Lung bleeding in horses is almost always more severe and frequent after racing or exercise.


Every time there is bleeding, scar tissue develops in the lungs. The blood vessels in the pulmonary circulation that rupture in the lung almost always break. They may also become blocked or cease to function properly after they rupture. The vessels may become stiffer if they are repaired. Scar tissue is less flexible than normal, healthy lung tissue. Even if damaged lung tissue is repaired, it doesn’t work as well and the horse’s ability to use his lung function and capacity are reduced.

Horse performance is limited by the lung. Even small impairments in lung function can have a significant impact on horse performance and reduce a horse’s chances of winning.

Horses will perform better if they have less bleeding. However, this may not only help in the short-term but also make it more likely that horses will suffer from inflammatory airway disease or chronic lung damage as a result of repeated bleeding episodes.


Horses can inhale more than 500 gallons per minute during intense exercise.

There are two major things that happen when a horse starts to exercise.

  1. Horses breathe more air to their lungs to extract carbon dioxide and bring in more oxygen.
  2. To help transport oxygen from the lungs into the heart and muscles, more red blood cells are transferred from the spleen through the circulatory system.

The horse’s stride, and the diaphragm, create a vacuum or negative pressure during inspiration. This forces air into the alveoli (air sacs deep within the lungs), where oxygen is transferred to the blood via small blood vessels called pulmonary capillaries.

Inhaling this much air at 500 gallons per hour creates strong suction forces on the alveoli. A thin membrane known as the pulmonary capillary skin separates the alveoli from the blood vessels in the lungs (pulmonary arteries). Because it is about one-tenth of the thickness of a human’s hair, this thin and fragile membrane is extremely efficient in transporting oxygen and removing carbon dioxide between the alveoli (pulmonary capillaries).

There is a strong negative pressure at the alveoli of the pulmonary membrane. However, there is also a strong positive pressure at the opposite end due to significantly higher blood pressure in the lung capillaries. The increased blood pressure can be attributed to increased red blood cell count and higher cardiac output. The blood’s oxygen-carrying ability is increased by increasing the red blood cell count. This happens because the spleen contracts, and releases its red blood cell reservoir into the bloodstream.

Warm-ups are vital because they ensure that there are more red blood cells available for competition.

Dramatic increases in heart rate are part of an increase in cardiac output. Horses can experience a heart rate increase of over 220 beats per hour (bpm) during intense exercise. This allows them to pump more than 75 gallons per minute. These forces can quadruple blood pressure in the lungs compared to its resting pressure. This is because exercise causes a significant increase in the positive pressure of the pulmonary capillaries than rest.

These opposing forces can cause Exercise Induced Pulmonary Hemorrhage when they are applied to the fragile pulmonary capillary Membran.

Inflammatory airway disease, bronchitis, and other inflammatory conditions can make the pulmonary capillary membrane more fragile, which increases the risk of bleeding.


The upper airway structures, including the nasal passages and larynx, are what prevent air from entering the lungs. The nose is the area that experiences the greatest resistance to exercise. The nasal passages are responsible for more than half of horse’s resistance to breathing in air.

FLAIR strips gently support the nasal passage to decrease soft tissue collapse due to narrowing of airways during exercise. This helps to reduce pressure differential so that the pulmonary capillary membrane will rupture less frequently.

Multiple clinical studies have shown that FLAIR Strips can reduce the risk of pulmonary capillary ruptures in horses and reduce lung bleeding.


Although bleeding can’t be stopped, and have been shown to reduce bleeding.

FLAIR Strips
FLAIR Strips do not contain any drugs and have been shown to reduce lung bleeding. Research has shown horses with EIPH who wear a FLAIR Strip after exercising have less blood cells than horses without the Strip. Because the FLAIR Strip can be used with any hard workout, it is a mechanical device.

Furosemide, also known as Lasix (or Salix)
Furosemide is a powerful diuretic which reduces blood volume, pulmonary vascular pressures and normalizes airflow. Furosemide decreases blood volume by increasing urine output, which in turn reduces fluid levels in tissues and other organs. Side effects include weight loss, dehydration, and electrolyte losses, especially potassium. It has been proven to lower EIPH in horses. A recent study showed that repeated administration of the drug reduces its diuretic effects. More studies are required to determine if furosemide’s effectiveness in reducing EIPH may be diminished by repeated administration.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!