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What is allergic rhinitis?

Created by Jeff Otjen.

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  • leaf green style avatar for user Andre F
    When we talk of eye allergies, are there other mechanisms that cause watery eyes (other than the blockage of the lachrymal duct) ? For example, do allergens enter the eye directly and generate histamine in the eye itself?
    (3 votes)
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    • leaf yellow style avatar for user adamzalaquett
      Yes, when the eye is irritated by allergens blood vessels will dilate making the white part of the eye look red, this will also cause the conjunctiva to produce more tears. This overproduction of tears may cause the eyes to water regardless of whether the nasolacrimal duct is able to drain them.
      (1 vote)
  • blobby green style avatar for user Reta2020
    Why do only some people get hay fever? Is it genetic?
    (1 vote)
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    • aqualine ultimate style avatar for user Sterre
      It's still not 100% understood why some people have allergies and some don't but it's definitely a combination of genetics and environment. According to the 'hygiene hypothesis', people who had more exposure to germs as very young kids are less likely to develop allergies because their immune systems develop better!
      (3 votes)
  • piceratops seed style avatar for user nor0001
    How is it that the mast cells in a normal person doesn't get activated? is IgE not present on a normal body's mast cell?
    (1 vote)
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    • duskpin seedling style avatar for user Alaska
      IgE IS present in a normal person's mast cells too. At , the speaker said that in a normal person's body, the reaction is minimal, and the cells DON'T overreact, as it isn't an infectious agent. But in a person suffering from Allergic Rhinitis, the cells overreact, as would happen in any allergy, and cause the other surrounding cells to get excited.
      (2 votes)
  • marcimus orange style avatar for user Ellie
    Wow so how do you get an allergic reaction to rhinitis? Just asking Bcause my brain literally just stopped working and I need to know this stuff. I am such a science nerd
    (0 votes)
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    • duskpin ultimate style avatar for user Betty :)
      An allergen enters the body, which your immune cells detect as a foreign potential pathogen. It binds to the igE antibody on your mast cells, and those, plus your basophils will release histamine. This causes the inflammation response, and thus, allergic rhinitis.
      (1 vote)

Video transcript

- [ Voiceover] So what is Allergic Rhinitis? The part of the word "Rhin" comes from the Greek root that means nose like in rhinoplasty or rhinoceros. And "itis" just means inflammation. So this is an inflammation of the nose. And "allergic" just means that it's caused by allergies. So let's go ahead and draw our nose here. This is the outside of the nose, but the inside of the nose is covered with a smooth lining. And that smooth lining is called mucosa. Mucosa lines everything inside your nose. But it's not just totally smooth in there. There're these bones that stick out that are called concha. They're called concha because they're kind of coiled like little snail shells. So we'll draw those in like this. This concha kind of stick out from the side of the wall of the nose. And they can take up almost all the space in there. But in order to figure out what's happening a little bit better, we have to zoom in. And we have to zoom in all the way to the level of the cells. So here I'm drawing some of the cells of the nasal mucosa. And these are big globular pink cells. But there's a couple cells in here that are different. And these are cells of your immune system. The ones that we are worried about, the immune cells in the nose that deal with Allergic Rhinitis, are called mast cells and basophils. So let's say this particular nose and this particular set of cells has Allergic Rhinitis. What exactly is happening? Well, in Allergic Rhinitis, like with any allergy, your body has an overreaction to some sort of stimulus in the environment. And that stimulus is called an Allergen. And let's take a little side note here and talk about the allergens that are common to people who suffer from Allergic Rhinitis. The most common culprit is pollen. And pollen can come from trees, or grass. In fact, hay can cause Allergic Rhinitis and it gives rise to one of the other terms called Hay Fever. Although technically, Allergic Rhinitis isn't a fever. Pollen also tends to be seasonal. In other words, some types of pollen are out in the Spring. Others in the Fall. And that gives rise to yet another term that's synonymous with Allergic Rhinitis or seasonal allergies. Other things that can act as allergens would be mold or animal dander. But basically anything that can get into the air that you can inhale can act as an allergen to somebody who suffers from Allergic Rhinitis. So let's say this nose in this group of cells are out there in the environment doing their thing breathing, and suck up something that's going to act as an allergen. So that allergen goes into the nose, and that allergen is going to come into contact with this mast cell over here. Being a mast cell or a basophil, on its surface it has a particular protein that's shaped a little bit like a "Y." And that protein is called an Immune Globulin. Which is shorten to "Ig." And this particular type of immune globulin is called "IgE." There are other types of immune globulins, "IgG" and "IgM" but for Allergic Rhinitis we're concerned with "IgE." This little grain of pollen, or whatever the allergen is. Let's assume it's pollen here. It's going to get bound by this "IgE" molecule. And that "IgE" molecule, just a protein sitting on the surface of this basophil, is going to alert that cell to its presence. On a normal person, the reaction that that cell has, should be pretty minimal. It's just a grain of pollen. It's not like it's an infectious agent that's going to go in and give your body all sorts of trouble. But in a person that suffers from Allergic Rhinitis, this cell overreacts and it overreacts big time. And when it sees that pollen grain it starts letting out little molecules into its environment that tell all the cells around it to get excited as well. So this whole group of nasal mucosa gets overreacted. The most common type of molecule that's used for signaling here, is called a histamine. So now that these immune cells are overreacting and causing all the cells around them to overreact to this allergen, we can predict what is going to happen inside the nose on a larger scale. Well, the first thing is that histamine is going to cause all sorts of problems with inflammation. And that could be really sever. The mucosa can thicken up big time and get really engorged and edematous, swollen. And that happens all throughout the nose. Because these basophils or mast cells aren't just sitting in one particular area. They're scattered everywhere. I'm going to draw some of this inflammation on these ridges in the nose, the turbinates. But it's happening kind of everywhere. And in addition to becoming swollen, this mucosa is going to start to overproduce mucus. And that mucus is going to drip down along the turbinates. It's going to drip down the sides of the nose here. It's going to form big drips that hang down inside your nose. It's going to pull on the base of your nasal cavity here. I'll draw a few other drips of mucus. Now, I'm drawing this mucus in green, but it's usually, actually clear. As you know, or anybody that suffers from Allergic Rhinitis knows, this can come right out your nose here. And of course, your nose is not an isolated thing. And as this mucus pulls in your nasal cavity, it's going to head down this way. And that is towards your throat. So you can cough up this stuff up as well. But your throat isn't the only thing that's attached to your nose. In fact, there's a tube that lives right about here that opens up just underneath this first ridge. Right about there. And as the mucosa swells up, it can swell that tube shut. And that tube is called the nasolacrimal duct. And it connects your nose to your eye. And its job is to drain the tears out of your eye and into your nose, where you don't even notice them. Now, when that duct gets swollen shut, the tears don't have anywhere to go. And that's going to lead to watery eyes. There's another tube that can be affected at the back of your throat. And that tube is connected to your ear. And it's called the Eustachian tube. And similarly, if the swelling gets bad enough, it can block off the Eustachian tube, and cause fluid to back up in this. And that's going to lead to symptoms with your ear. Particularly, stuffiness and decreased ability to hear. Of course there's also nerves in your nose. I'll draw one of the nerves going off to the turbinate here. These nerves ultimately end in your brain. And as they get inflamed with all the processes that's happening in your nose, they become irritated and send signals to your body. Particularly, the signal to sneeze. And then if the swelling continues to get bigger, and more pronounced, and more pronounced, it can actually completely block off this entire nose. And when that happens, even air can't get by. And when air can't get by, breathing becomes a problem. So let's recap the symptoms. First, you get swelling and congestion. If you block off the nasolacrimal duct, you can get watery eyes. If you block off the Eustachian tube, you can get stuffed up ears. And that nasal mucosa is continually making mucus. And that causes nasal drip. The irritated nerves cause sneezing. And the blocked air passages, leads to difficulty breathing through the nose. And these symptoms are going to vary from person to person. Some people's overreactive immune systems are severely overreactive. These symptoms are really, really bad, or they're happening all the time. Other people may just have a nasal drip and that's all. Some people's anatomy may be such, that their nasolacrimal duct is easily blocked by just a little bit of swelling. And that can lead to really bad watery eyes. But not much else. It all depends on the person. It can happen for a few days if you're exposed just briefly, or it can happen year-round if you're allergic to many things that are always in your environment. Additionally, sometimes it's really easy to figure out what it is. Sometimes it's really hard and you can't ever pin down exactly what it is. But, if you remember the underline principles of an over reactive immune cell sitting in your nose, and you know a little bit about the anatomy of the nose, you can predict all the symptoms that happen in this situation.