Exercise Induced Pulmonary Haemorrhage (EIPH)

Exercise Induced Pulmonary Haemorrhage (EIPH)
5 July 2017 | Foran Equine

Based on surveys of horses examined endoscopically following racing, around 40% to 70% of horses have been reported to have blood in the trachea following a single post-race examination.

Exercise induced pulmonary haemorrhage (EIPH), or “bleeding”, refers to the presence of blood in the airways of the lung in association with exercise and may lead to the impairment of lung function. In the majority of cases EIPH is not apparent unless an endoscopic examination of the airways is performed following exercise. However, a small proportion of horses may show bleeding at the nostrils after exercise, which is known as epistaxis.


Based on surveys of horses examined endoscopically following racing, around 40 to 70% of horses have been reported to have blood in the trachea following a single post-race examination.

Clinical Signs & Diagnosis

Poor athletic performance, frequent swallowing and coughing in the immediate post-exercise recovery period may indicate that a horse has experienced EIPH. A definitive diagnosis can only be made by endoscopic examination of the trachea and/or a tracheal wash. In the case where no blood is visible in the trachea, EIPH in the small airways may still be present and can be confirmed by a broncho-alveolar lavage (BAL). Because the degree of haemorrhaging varies between horses, it is useful to use a combination of these techniques to accurately diagnose EIPH, and to determine the amount of bleeding within the lungs.


A variety of different causes of EIPH have been proposed. These include high pulmonary vascular pressure, upper airway obstruction, mechanical trauma, lower airway obstruction, inflammation, abnormalities of blood coagulation, inhomogeneity of ventilation and locomotory trauma. To date most theories have been unable to explain why EIPH occurs in the dorso-caudal lung and the pattern of progression in a cranial direction.


Preventing recurring episodes of ‘bleeding’ is important in keeping a horse healthy. The environment should be addressed ensuring that there is plenty of ventilation and that good stable hygiene is practiced. Exposure to fungus, mould spores and other potential allergens should be avoided, and forage and bedding should be of good quality and without contaminants.

Exercise and conditioning programs should be developed towards building on a horse’s fitness gradually, focussing on stamina and strength before progressing to speed and intensity, and so enhancing capillary network and blood distribution.

Diets high in protein may also be a contributing factor. Excess protein is broken down into urea and expelled in the urine. If confined to an area where the ammonia fumes are inhaled over a period of time, horses may develop irritation in their airways and lungs causing them to bleed when exercised. Forage fed from hay racks cause horses to inhale spores and dust which can irritate airways and lungs.


A wide variety of treatments have been used or suggested for the management and treatment of EIPH, including resting, anti-inflammatories, bronchodilators, anti-hypertensive agents, snake venom, aspirin, diuretics, nasal strips, concentrated equine serum as well as nutritional supplements such as vitamin C, vitamin K, bioflavonoids and omega-3 fatty acids.

  • Vitamin C

It is very important in collagen construction and maintenance in blood vessels and is responsible for maintaining iron in its reduced state thereby preserving its numerous iron-containing enzymes which are responsible for the strength and elasticity of blood vessels and capillaries. Vitamin C is a potent natural antioxidant. Vitamin C is essential in the process of forming new red blood cells, wound healing, tissue repair, enhanced immune function and providing a mild anti-inflammatory action. Vitamin C is a water soluble vitamin, like the B complex group, and is rapidly absorbed & excreted, so supplementation may be recommended.

  • Vitamin K

Vitamin K is involved in the blood clotting process. Vitamin K is a fat-soluble vitamin. In horses, forage sources and the bacterial activity in the gut upon ingestion of forage produces vitamin K.

  • Bioflavonoids

Citrus bioflavonoids are found in fruit and their rinds. Bioflavonoids have numerous functions in the body, and are closely linked to the functions of vitamin C. They are widely used to reduce bruising in humans, and have a valuable effect to maintain the strength and function of capillaries. Bioflavonoids are also potent natural antioxidants which scavenge free radicals during hard exercise. They also help to potentiate the immune response, are anti-inflammatory agents and have an anti-histamine effect.

  • Omega 3 fatty acids

Omega 3 fatty acids are important in the equine diet because they are the only forms of fat that the horse cannot synthesise in the body, meaning that they must be present in the horse’s diet in order for the horse to benefit from them. A horse deficient in these essential fatty acids will likely have a dry coat, skin and hooves, reduced immunity, increased tendency for allergies and/or exaggerated immune responses, and stiffer red blood cells that do not fit through capillaries as easily as they should. The process of making hay destroys most of the omega 3 fatty acids found in fresh grass. Cereals are relatively low in omega 3. Cod liver oil and flaxseed oil are excellent sources of omega 3.