 Do you love smelling flowers? Well, I do too, but do you know every time we smell a flower? There are high chances that the pollen in the in the flower might get inside our nose So should we be worried about that? Well, most of the time when the pollen enters nothing actually happens. It doesn't affect our body But in some people like in case of my brother Ram Every time he smells a flower. He sneezes like crazy and He also gets this watery eyes runny nose and redness and swelling around his nasal area Now since Ram's body reacts in a very different way towards a non-harmful substance like a pollen Ram is said to have an allergy Allergy towards pollen now anything that triggers an allergy is called an allergen So this pollen pollen is an allergen for Ram But it is not an allergen for me because I don't get all these symptoms when I smell a flower Now the question is what is happening different in case of Ram? Because we are closely related we are siblings and we share fair amount of our DNA So why is Ram's body reacting in a different way than mine? Let's find out Let's begin by talking about the word allergy Allergy comes from a Greek word, which means change in reaction Now what reaction is it talking about? It is talking about the body's immune cells reaction The immune cells somehow tend to become over sensitive towards non-harmful substances And that reaction of our immune cell towards non-harmful substances causes an allergy So allergy is actually the weird reaction of our immune system Our immune system somehow tends to behave in a very weird way So to see how the immune system behaves differently how about we check my immune system And then my brother Ram's immune system every time we inhale some pollen So this is me I am not allergic to pollen and as you can see I have inhaled some pollen Now what will happen after that? The pollen will first encounter the hair that is present in our nasal passage So these are the hairs And this one here is the pollen So the pollen will try to enter our nasal passage So the first obstruction will be the hair And then beneath the hair will be a dense mucus layer So these are the mucus So some pollen will be trapped by the mucus But let's say the pollen has passed the mucus layer as well Then beneath the mucus layer will be the epidermal layer So these are our epidermal cells, the outer layer But the pollen is so stubborn that it has passed all these layers And have gone deep down under these epidermal layer So let's say here is the pollen But the pollen has no idea that our body has got defensive cells Which we call immune cells And this pollen will now encounter our immune cells Now this is where the difference is The immune cells from here on will start acting differently in me And in case of my brother So let's see how my immune cells behave So let us consider that somewhere here the pollen has got inside the epidermal layer So as soon as it enters it will face our immune cells So this one here is a pollen And this is the immune cells Now the immune cell will phagocytose the pollen Or we can say the immune cells will eat the pollen Now after they do that they will release some chemicals in this in this vacuole And it will destroy the pollen particles It will break down into small small non-functional pieces And that is the end of the pollen story inside my body Simple, right? Now let's see what happens differently in case of my brother Ram So here is Ram He is allergic, allergic to pollen Okay? In case of Ram the immune cells after eating up the pollen This plays the pollen to the other immune cells Let me show you how They do it with the help of a special protein called Amid-C class 1 Now the question is Is this protein not made in my body? The answer is yes It is present in my body my immune cells as well In fact it is present in all the cells of our body But why is it displaying the parts of a pollen to other immune cells in case of Ram But not in case of me The answer lies in the structure of the Amid-C molecule This is the Amid-C molecule Which has this variable region here And this one here is the pollen Now this variable region is formed from a random shuffling of a piece of DNA Or we can say a gene that codes for the variable region of Amid-C It randomly shuffles and forms this variable region So it is sheer luck that the variable region of Ram Somehow could attach to this pollen But the variable region of Amid-C in case of me Did not bind to a pollen So this is the first step where both of our immune system acted in a different way So what happens after that? Why is this playing of a pollen by an Amid-C molecule a big deal? This is a big deal because it presents this pollen particle to the T cells The T cells then sends a strong signal to B cells to form antibodies against it Here you will not understand where these T and B cells have all come in from Until you have watched the videos of what B and T cells are and how they react Well these are all immune cells They have their own very important functions in the immune system And as soon as all these cells get activated here As soon as this B cell gets activated It will produce a special type of antibody called IgE That is Immunoglobulin E Now let me tell you that this IgE is not the very common type of immunoglobulin produced by B cells It normally produces IgG or IgM kind of antibodies Now there are videos that talks about all these different type of antibodies I won't elaborate it here but these are antibodies produced against a specific type of foreign invader or antigen Now here as IgE is produced this IgE is produced only during allergic reaction Now what this IgE does and why is it so different? Well this is because the other immunoglobulins which are produced by B cells through a plasma cell Goes and binds to the foreign invader or to the antigen directly But here the IgE it goes and binds to a special type of immune cell called the mast cell And this mast cell have special receptors on top of it that has very high affinity for IgE antibodies And IgE goes and binds to these mast cells Now this mast cells are said to be sensitized Now can you guess why? Well this is because the mast cell initially had no clue what these pollens were But now with the help of specific IgE molecule that has come and docked on to this mast cell This mast cell has now become very very sensitive towards this pollen Okay let me tell you another thing about this IgE molecule This immunoglobulin E molecule has a very short half life But as soon as it goes and docks on to this mast cell its lifespan increases It can now stay potent for around 2-3 weeks And during that time if this pollen happened to enter the body of Ram again Can you guess what can happen? Well this time the pollen will be taken up directly by the IgE antibody that is present on top of the mast cells And as soon as the pollen binds to the IgE molecule the mast cell ruptures And as you can see it releases all its content in the vicinity Now before I tell you what happens next let me clear the board a little bit Alright so now as you can see this mast cell have released some chemicals So what are these chemicals among the many different type of chemical it releases? The very potent and the most important one is the histamine So what this histamine does is that it widens the blood vessel So this is the normal diameter of a blood vessel So as you can see it widens the blood vessel and then also causes the cells that makes up the blood vessels to shrink So as those cells which we call endothelial cells as those cells shrink The blood vessels becomes permeable and the fluid rushes out of the blood vessels Causing swelling and redness in that area And that is why Ram gets that redness and swelling in the nasal area And on top of that histamine increases the glandular secretion So let me write down gland secretion And in this case it increases the secretion of the mucus glands and therefore Ram gets a runny nose And all these causes a lot of irritation in the nasal passage of Ram and that causes continuous sneezing Now along with histamine some other chemicals are also released by the mast cells And few of those chemicals also attracts more mast cells to come into that area and burst themselves And that adds on to the misery that this mast cell was already causing And that is how my poor brother Ram gets an allergy from pollen Now let's talk about the remedy and the cure for allergen Well sadly we still don't have a cure for an allergy but we do have drugs that stops the action of histamine Or stops the action of other chemicals that's released by the mast cells But that do not provide a permanent cure towards an allergy The next time Ram inhales a pollen the same chain of reaction will occur again The mast cell will be released and then he will have to take a drug to counteract all those chemicals So the best piece of advice in case of an allergy is avoidance If you are allergic to pollen avoid smelling a flower If you are allergic to peanuts do not eat peanuts Well doctors have also come up with another treatment where very small doses of an allergen is injected Over a long period of time so that the body's immune system at one point of time stops reacting to that allergen