Why Do Some Thoroughbred Horses Get Nose Bleeds?

Why Do Some Thoroughbred Horses Get Nose Bleeds?

Health & Safety

If you're into horse racing, you may have heard how certain thoroughbreds burst blood vessels when they take part in a race. Some thoroughbreds are prone to doing this more often than others and are known as "bleeders" but why do some horses bleed and which blood vessels are affected and if you re-home a thoroughbred would you have problems with them bleeding?

For centuries, man has known that some racehorses suffer nose bleeds when they race or sometimes this happens after the race has finished. However, it is only very recently that studies have shown that it is not in fact, blood vessels in their noses that get damaged but rather the problem is in their lungs. With this said if you are thinking about re-homing a thoroughbred horse, you would need to understand the difference between a nosebleed that's bought on by exercise which is a condition known as EIPH (exercise-induced pulmonary haemorrhage) and one that happens when a horse is at rest or not being exercised and which could be caused by something else.

When horses suffer nose bleeds at rest, the bleeding originates in their upper airways and because there are a couple of conditions that bring on a nosebleed which in horses, can be a very serious if not fatal which is why it is crucial to call out the vet to make sure neither of these are the cause of their condition.

Do Many Horses Suffer From the Condition?

Very few racehorses suffer from nosebleeds, however, back in the eighties after a study was carried out all over the world, up to 75% of racehorses were seen to have blood in their windpipe (trachea) after they had been racing. As a result the condition became known as exercised-induced pulmonary haemorrhage. In the UK, it is thought that just over half of horses do in fact have blood in their lungs after they have taken part in a race.

Further studies showed that the older the horse happens to be, the more likely they were to suffer from EIPH and that it is not only racehorses that are affected by the condition. Arabs, Appaloosas and Standardbreds too can be affected. Eventers, polo ponies and show jumpers also suffer from EIPH but endurance horses rarely suffer from the condition. The good news is that although the percentages may seem high, in most cases the blood loss is very small which means the condition often goes unnoticed.

Why Do Some Horses Bleed?

Nobody actually knows what causes EIPH but it is believed that a form of respiratory disease might be present which causes bleeding in the lungs. However, another train of thought is that any bleeding found in the lungs is inevitable when a horse is asked to do strenuous exercise even if their lungs are healthy. Other people think the condition is caused by a condition known as "pulmonary capillary stress failure".

Does Bleeding Affect Performance?

It would be natural to think that a horse suffering from EIPH would not be able to perform as well as they should, but in reality there is no evidence of this being the case whether it's a racehorse, polo pony, eventer or show jumper. With this said, if a horse is severely affected their performance does suffer to a certain degree although the jury is still out when it comes to actually knowing if it's the condition that's responsible or some other reason.

Can the Condition be Treated?

The first thing a vet would need to assess is whether or not the condition is seriously impacting a horse's performance as to whether or not they would decided to treat EIPH. It is usually only horses that are considered to be serious "bleeders" that would need to be treated and of the various treatments available, the most effective one seems to be diuretic frusemide which goes by the brand name Lasix.

What's The Prognosis?

For horses suffering from frequent and severe bouts of EIPH, the prognosis is always pretty guarded. Some horses have one or two really bad nosebleeds and then never suffer from them ever again. When a racehorse is considered as being a "repeat bleeder" they are usually retired from the racecourse and very often are re-homed with people outside the racing industry. These lucky horses normally get to live out their lives very often competing in a different discipline and only occasionally suffer from a nosebleed and one that's never that severe. However, it is always best to talk to a vet should you have re-homed an ex-racehorse that is a known "bleeder" and they start bleeding excessively.


If you are thinking about re-homing an ex-racehorse and one that was retired due to the fact they suffered from EIPH, it is not the end of the world because although they may occasionally suffer a slight nosebleed, you don't have to go into a panic. The majority live out their lives quite contentedly as either "happy hacks" or competing in other disciplines. However, it is always better to discuss the condition with your vet so they can examine your horse to make sure nothing else untoward is going on.



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