Nosebleed (epistaxis)

Epistaxis means bleeding from the nose and is relatively common in horses. If your horse has a nosebleed dont panic! The nasal passages are full of blood vessels, so it can look like a lot of blood is coming from the horses nose. Most minor nosebleeds stop within 15 minutes, so any bleeding that lasts longer than this should be seen by your vet.

Nosebleeds can range from a small amount of blood or bloody discharge at the nostril to a significant amount of blood coming from one or both nostrils; blood seen at the nostrils may be coming from one or more different places.
In the simplest case a horse may knock his nose and burst some small blood vessels in the nostrils, in this situation the bleeding should not be severe and should stop quickly. On the other hand, blood seen at the nostrils of a racehorse for example, after a hard race, is usually coming from the lungs, a condition called exercise-induced pulmonary haemorrhage (EIPH). Viral infections in the nasal passages may also cause the horse to have a nosebleed or a bloody nasal discharge. Bacterial infections of the teeth and sinuses may also result in a bloody (usually smelly) discharge.
Ethmoidal haematomas are another cause; these are masses similar to a large blood clot growing in the nasal passages which can cause nosebleeds. These masses may need removing or shrinking using certain chemical or laser treatments.
Gutteral pouch mycosis is by far the most serious cause of nosebleeds. Gutteral pouch mycosis is caused by a fungus growing in the gutteral pouch. The guttural pouches are blind ended sacs near the horses pharynx. Several important nerves and vessels run through these, including the internal carotid artery. As the fungus grows it may eat away at the wall of the vessels and eventually cause them to rupture causing the horse to bleed. Treatment of this disease often includes surgery to stop or prevent the bleeding.

The most important course of action if your horse has a nosebleed is not to panic! The nasal passages are full of blood vessels and so it can look like a lot of blood is coming from the horses nose. Most minor nosebleeds should stop within 15 minutes. If your horse has a small amount of blood at the nostrils and is showing no signs of persistently bleeding it may be that they have just knocked their nose, however if you are at all concerned call your vet.
If your horse has a lot of blood coming from one or both of its nostrils you should make sure the horse remains quiet and still and call your vet immediately.
If your horse has several nose bleeds over a period of time you should call your vet and have your horse examined.
When you call your vet it is very useful to give them some history about the nosebleed, including when it first started, is there an obvious reason for the bleeding, e.g. has your horse just knocked its nose, how fast the blood is dripping out of the nose, if it is coming from one nostril or both, if this is the first time your horse has had a nosebleed, if your horse has recently been exercised or been unwell, or if the horse is looking sick or distressed.

The first thing your vet will do is examine your horse very thoroughly and they will ask you lots of questions about your horse to try and work out why he has had a nosebleed. Your vet may recommend that your horse has further tests to determine where the blood is coming from.
Further tests may include x-rays of your horses head which can help to detect sinus infections and ethmoid haematomas, and endoscopy to examine the nasal passages and ethmoids. Endoscopy involves the use of a flexible camera which is inserted up the horses nose to view the nasal passages and ethmoids. Endoscopy is also used to diagnose guttural pouch mycosis as the camera can be driven into the guttural pouch to look for fungal disease.
If your vet suspects the blood to be coming from your horses lungs they may want to use endoscopy to examine the horses lungs and large airways as well as collecting samples of fluid from the lungs which can be examined under a microscope for the presence of blood.