Who hasn't had a nosebleed at some time in their life? You might walk into a door, have a silly fall, an injury that hasn't healed, the central heating may be blasting away, there could be a change of air pressure, your blood pressure may be sky high and bingo! You see the blood and start to panic.
"Nosebleeds normally have a good outcome and are resolved with no problem in most cases. What happens is that this is an area with a lot of small veins, which can also break quite easily, and there always seems to be an awful lot of blood," say sources at Cruz Roja (the Spanish Red Cross).
In fact, only one in ten nosebleeds are considered serious. "If they are serious, it is either because there is so much blood or because they are repetitive and occur every week or even every day," according to the Spanish Society of Otorhinolaryngology and Head and Neck Surgery (SEORL CCC).
The bleeding normally starts in front of the septum inside the nostril and it happens suddenly. It usually stops within a few minutes or with a little pressure being applied.
Bleeding from the back of the nasal cavity, just behind the nose, is less common and can be more dangerous because the blood can go down the throat, the Society says.
"Also, in those cases the bleeding is more difficult to stop," explains Dr Iñigo Ucelay Gallastegui, who is an ENT specialist at the IMQ.
There are many causes of nosebleeds or epistaxis and they can be associated with age. "Children, for example, often get them because their nose has been knocked, and because they pick their nose more frequently and cause injury, or because of congestion, or mucous... while in adults the most common cause of a spontaneous nosebleed is high blood pressure," says Dr Ucelay.
Sudden nosebleeds can be scary, but they are usually over quickly. Apart from blows and high blood pressure, the nose can also bleed because of sudden changes in air pressure, any type of surgery that involves manipulating the nostrils (nasal endoscopy, nasogastric tube or after nasotracheal intubation, for example), dry atmospheres caused by central heating or air conditioning, nasal inflammation through pathologies such as dry rhinitis, or any anticoagulant medication, which could even be aspirin," says the Spanish Society.
Pregnant women are also more prone to nosebleeds because of the increased nasal blood flow as a consequence of hormonal changes.
"Nosebleeds which occur repeatedly, in frequency and volume, can be a sign of tumours in the nasal passages, so in those cases it is important to have them checked out by a specialist," say the experts.
One of the biggest mistakes people make in first aid is with nosebleeds, according to Cruz Roja. Whether the person is an adult or a child, if their nose starts to bleed the advice is to incline the head slightly forward - not back.
The next step is to apply pressure with the index and middle fingers - like a pincer - on the sides of the nostrils for five minutes. The patient should breathe through their mouth. Most nosebleeds can be stopped this way. Ice or cold compresses on the nose can also help to control bleeding.
Another mistake that people often make is to place cotton wool or tissue inside the nose, to block it. Nobody should ever do this, because there is a risk of a blood clot forming.