What are nosebleeds and why do they happen?

TW- This post is pretty much entirely about blood/nosebleeds, so if you get squeamish about that kind of stuff then this might not be the article for you!  

Nosebleeds! Not as scary as they may seem! (source)

One second, you're fine, next second, blood is flowing out of your nose. You have a nosebleed: annoying, messy, and worst of all seemingly unpredictable. But why? Why do nosebleeds even happen? Before you can answer that question, first you have to ask: What even is a nosebleed? 

                                                

Nose structure (source) 

Epistaxis is the medical term for nosebleeds. Epistaxis originates from Greek and directly translates to "a dripping," specifically a dripping of blood from the nose. You have to understand the general structure of your nose and why nosebleeds can be common in perfectly healthy people. This image may look confusing with all the intricate structures, but for the sake of simplicity concerning this blog's topic, we're only going to focus on the anterior ethmoidal artery and posterior ethmoidal artery. These arteries are where nosebleeds start, and the severity of the nosebleed also depends on which location it's starting from. If you look at the image above, you'll see that there are a lot of blood vessels in the tissue that lines the inside of your nose. Take note of this- it's important! Think about it- with all these blood vessels lying so close to the surface of the tissue inside your nose, even the smallest level of tampering can trigger some sort of damage to one or many of the blood vessels. So for now, just understand that all nosebleeds are in some form or another the result of damaged blood vessels that line the tissue on the inside of your nose. 

Anterior vs Posterior nosebleeds (source) 

The top image shows what happens when a nosebleed stems from the anterior artery and the bottom image shows what happens when a nosebleed stems from the posterior artery. 

Anterior arteries are the most common- if you've ever had a nosebleed, you've probably had an anterior nosebleed. As you can see, in an anterior nosebleed the blood vessels break in the vascular network called Kiesselbach plexus- but you can just think of this as "front part of the nose." Because the small blood vessels are in the front, the blood leaves straight through the nostril. So next time you blow your nose a little too hard and blood comes out, just know you're dealing with a completely fine and not serious anterior nosebleed. 

On the other hand, posterior nosebleeds are a bit harder to detect. As you can see in the image above, these types of nosebleeds are the result of larger blood vessels in the back of the nose. Because the location of this type of nosebleed is closer to the throat that it is to the nostrils, the blood flows down the back of the throat. Posterior nosebleeds are more serious, and usually are the result of head or nose trauma or various medical conditions. 

Now that you understand the basics of what's actually happening when you have a nosebleed, let's tackle the actual factors that damage the blood vessels. 

First, let's go back and focus on anterior nosebleeds, since they're the most common. Again, these start in the front part of the nose, where blood vessels are small and right in the surface of the inner tissue of the nose. Since these blood vessels are so close to the surface of the inner lining of the nose, completely unintentional triggers like blowing your nose too much, picking your nose, or even scratching your nose can actually result in damaged blood vessels, and therefore a nosebleed. Other than those, there are also environmental factors that trigger the damage or breakage of blood vessels- most commonly this is dry air. Dry air causes the nasal membrane (which is the tissue lining the inside of your nose) to become dried out and cracked; these cracks either directly damage the blood vessels or they expose the delicate tissue covering the blood vessels to various other factors (namely tissues/wipes or your fingers) that are then able to further disrupt the blood vessels, prompting blood flow. 

At a cellular level, here's what happens when a blood vessel gets damaged. 

Damaged blood vessels (source)

Immediately following the break of a blood vessel, red blood cells are able to flow out of the opening and into other parts of the body. In context with nosebleeds, think of this as the first few thin drops of blood that come out of your nostril. But how do these nose bleeds stop? The answer is blood clots. Blood clots essentially plug the damaged blood vessel to prevent more blood from leaving it. Blood clots are formed through the blood clotting cascade, or the coagulation cascade. This is a process by which a blood clot is formed in response to an injury through a cascade of proteins called clotting factors. As red blood cells initially leave the blood vessel, clotting factors then convert the protein prothrombin into its active form thrombin, which is a protein that helps blood to clot. As a platelet plug begins to form at the break of the blood vessel, the thrombin protein converts fibrinogen to fibrin- fibrin binds together platelets and other proteins to form a blood clot to stop the blood vessel from bleeding. The development of a clot is what stops your nosebleed. In fact, the blood clotting cascade that's responsible for creating a blood clot is what prevents people from bleeding out from any injuries spanning from nosebleeds, to serious open wounds, or even just from a simple paper cut. 

Now that you understand how important the blood clotting cascade is to preventing people from bleeding out, you might start to wonder what would happen if the enzymes integral to the clotting cascade didn't work. If this were the case, the result would be hemophilia. Hemophilia is an X-linked disorder, meaning that the genes responsible for the blood clotting factors are on the X chromosome, that involves mutated enzymes. Because the enzymes, or the clotting factors, involved in the blood clotting cascade are mutated, blood clots can't form properly and the result is excessive bleeding (either internal or external) from any injury. Look at the image above; normally, after some sort of injury or impact to a blood vessel (even as minor as a soccer ball to the knee), blood clots form to prevent blood vessels from bleeding out. However, when the clotting factors are mutated, these blood clots can't form and bleeding occurs anyway. Hemophilia cannot be cured because it is an inherited disorder that parents can pass on to their children. Although there is no medical cure for hemophilia since it is a genetically inherited disorder, treatment involves an injection of the missing and functioning blood clotting factors. People with hemophilia can actually learn how to perform these injections on their own, and doing so on a regular basis has proven to be effective in preventing bleeding episodes.

This is what hemophilia can look like (source)  

Another genetic disorder related to nosebleeds is Hereditary Hemorrhagic Telangiectasia (HHT), which occurs in 1 in 5,000 to 1 in 10,000 people. People with HHT have fragile blood vessels or under developed blood vessels. Since nosebleeds are the most common symptom, most people don't even realize they have HHT until later in life. However, over time HHT can cause blood vessel problems in other parts of the body such as the lungs, gastrointestinal tract (the GI tract includes all of the major organs of the digestive system, so the esophagus, stomach, and intestines), brain, skin, or liver. Blood vessel abnormalities caused by HHT can show in either small or large blood vessels: small blood vessel abnormalities are seen in the skin, in either the hands, face, nose, mouth, or lips, and are called telangiectasias. Large blood vessel abnormalities are called arteriovenous malformations, or AVMs. AVMs can occur anywhere on the body, but are most commonly found in the nose, lungs, liver, gastrointestinal tract, and liver. 

HHT is an autosomal dominant disorder and most cases of the disorder are linked to mutations in the two genes ENG and ACVRL1. The ENG gene codes for the protein endoglin, which helps bind growth factors, proteins, and endothelial cells (which are cells lining the insides of blood vessels) to develop blood vessels. On the other hand, the ACVRL1 gene codes for a protein called activin receptor-like kinase 1. The activation of this receptor protein by its ligand is also involved in the development of blood vessels. That being said, when mutations in these genes occur, blood vessels are not able to develop properly, which results in HHT. 

Signs and Symptoms of HHT (source) 

Let's go back to nosebleeds that are not the result of genetic inheritance. Have you ever had a nosebleed just keeps coming back over and over again? The chances are that you are repeatedly irritating the blood vessels inside your nose, and in doing so you're interfering with their repair process. 

More damaged blood vessels- except this time it's kind of different (source)

Although this image is fairly similar to the previous image showing the repair process of a damaged blood vessel, you'll notice that this image shows an additional few. stages in which the blood clot that's supposed to stop bleeding ruptures and bleeding continues. Sometimes bits of blood clots can actually come out of your nose too. What I mean by that is that blood clots slowly leave your nostril- it's arguably one of the most uncomfortable feelings ever. 

I've probably said it a million times now, but given how close they are to the surface of the nasal membrane, blood vessels are particularly vulnerable in the nose. Especially if the blood vessels have already been damaged, meaning especially if you've just recently had a nosebleed, the smallest of disruptions can break the fibrin bonds holding the blood clot together, allowing blood flow to start again. This results in yet another nosebleed. If you've gotten multiple nosebleeds within several days, it's most likely the result of one broken blood vessel or a group of broken blood vessels that keep getting re-damaged. Typically, broken blood vessels take one to two weeks to completely heal. Note that this is focused on anterior nosebleeds and not posterior nosebleeds (the healing process of posterior nosebleeds complicates based on what kind of trauma caused it). 

What can you do to prevent nosebleeds? As someone who both historically and currently deals with nosebleeds on a pretty regular basis, I'd suggest buying a humidifier to bring more moisture into the air- it's actually very helpful! 

Potential humidifier option that I would support anyone purchasing (source)

Thanks for reading!