Hey there everyone! Welcome back to Seeker+, where we go in depth on the topics that fascinate,
bemuse, and amuse us. I’m your host Julian and where I am in North America, spring is here! The
birds are chirping, the flowers are blooming, the seasonal allergy sufferers are miserable.
[Sneeze]
About 7 to 8 percent of people in the U.S. suffer from hay fever and for many of them,
right about now is the start of the bad times. They’re bracing for an onslaught
of symptoms like constantly runny noses, red itchy eyes, fatigue, and sneeze after sneeze
after sneeze. Who knew that plants could be practically murderous? Aside from Mark Wahlberg
in that one weird M Night Shyamalan movie, The Happening,
you know the one I mean?
Still hay fever is just one variety of
allergies. People can be allergic to certain foods or medicines or insect stings or animals. Some
allergic reactions can do more that make the sufferer long for the sweet embrace of death,
it can actually kill them. So, be careful what you wish for. In this Seeker+ we wanted to
take a look at allergies. What’s happening in the body that causes this reaction? Why
do some people have allergies while others get to live blissfully clear-headed lives?
And how do allergy treatments work? When looking at the variety of things
that cause allergic reactions and how wildly different the reactions can be,
I started to wonder why they all fit under the umbrella of allergies? Well it turns out it’s because
the definition of an allergy is pretty broad. Allergic reactions happen when the body’s immune
system overreacts to something that’s normally harmless. These substances are called allergens.
For people with allergies, their first exposure to an allergen may be harmless. On the outside,
everything might look normal. But on the inside their body is ringing alarm bells and gearing up
for future invaders. Days or even years can pass between the first exposure and the first allergic
response. Really you never know if you might have an allergy and just don't know it yet, which is
something we’ll talk about later. Some people may seem as though their bodies are reacting the very
first time they’re exposed to an allergen, but they may have unknowingly encountered it before
through their skin, or when they were babies being breastfed, or even in the womb. But for
their immune system to respond, it must have had a run-in with the perceived threat before.
After that initial encounter, a person with allergies will start producing more of a
specific antibody inside their… body. Now to be clear, antibodies are incredibly useful parts
of your immune system. They’re little Y-shaped proteins that are part of your body’s adaptive
immune system, which can learn to recognize new threats and destroy them. Antibodies are also
known as immunoglobulins and humans have five varieties: IgG, IgA, IgM, IgD, and IgE. While
they all have that Y-shape in some arrangement or another their exact structures differ,
they’re found in different parts of the body, and have different roles and functions. IgG are
the smallest and the most common, making up about 75% of your antibodies. They help fight viruses
and bacteria, and can give developing fetuses an immune boost from their birthing parent
while in the womb. IgA are found in serum as well
as spit, sweat, and tears. They’re also in the gastrointestinal, respiratory, and genitourinary
tracts. IgM are the first antibodies made when an infection is detected. And we’re not totally sure what
IgD do. And finally there’s IgE, and these are the jerks responsible for a lot of allergic reactions.
Now normally when something harmful enters your body it’s detected by a type of white blood cell
known as a B-cells. You have about a trillion B-cells in your body and because of genetic
shuffling each one has a different IgM antibody on its surface that reacts to a specific intruder. If
a B-cell’s antibodies bind to something, the B-cell starts dividing and creating a clone
army much like Count Dooku. There can be millions of cloned B-cells, which transform into plasma
cells that pump out antibodies at a prodigious rate; each cell can produce as many as 10,000
antibodies every second. These antibodies swarm invaders and can either neutralize them directly,
or tell other cells in the immune system to come take out the trash.
Anything that makes your immune system generate antibodies is called an antigen. Get it, anti gen?
For people with allergies the trouble starts when B-cells that are supposed to make IgM antibodies
start making IgE antibodies instead. Certain antigens and certain ways antigens make contact
with the immune system increase the likelihood of switching to IgE production. These IgE antibodies
are still sensitive to that antigen, and on top of that they bind to other cells like mast cells and
basophils. When IgE binds to both an antigen and these other cells, it can trigger the creation of
even more IgE from B-cells. Mast cells and basophils also can release inflammatory mediators, including
histamine. This is the last domino to fall in this long sequence of cascading misery. Histamine
increases blood flow to wherever the allergen is and then dock with receptors that cause symptoms
allergy sufferers know all too well. In the nose it causes mucus production. It leads to itchy red
eyes. In your skin it can cause hives or eczema. In the gut it can cause vomiting and diarrhea.
All of these symptoms really have the same goal: get whatever the IgE is reacting to
out of your body. If histamine has to make you blow your nose or scratch like mad or wretch up
your lunch, so be it. Histamine, along with other substances released by mast cells and basophils,
can cause more than just discomfort. In some cases their effects can combine,
dropping blood pressure, speeding up heart rate, and constricting airways. This full-body rapid
meltdown is known as anaphylaxis, and if not treated quickly the results can be deadly.
So, what gives, IgE? What exactly was your whole plan here? Well like many things that lead
to horrible consequences, it started with good intentions. IgE antibodies are specialized at
fighting parasites. They came in handy back in the early days of humanity when we encountered
parasites regularly. In fact they were probably necessary for our survival, and still are for
people who live where parasites are more common. But without a serious foe, IgE antibodies are like
that high-strung dude at a bar just looking for an excuse to fight anybody. Sometimes that happens
to be cat dander. I mean you could count cats as parasites, they do just eat your food and give you
almost nothing in return. I’m kidding, cat owners, I have a cat who I love, even though I am
allergic to cats. If that isn’t love, I don’t know what is. And besides, people are allergic to dogs
too. So why is that? Why are some people allergic to certain animals or foods while others aren't?
We’ll get into that in our next episode. For now, I hope you enjoyed this topic,
especially if you’re an allergy sufferer like me who wishes they could just explain to their
immune system that everything’s chill, you don’t need to go so hard. Let me know if you’re in the
puffy-eyed gang or if you’re not and you think you’re just so much better than us. Because I
have news for you... you might be joining us at some point. Yeah,
yeah, who's laughing now? And sneezing? And rubbing their eyes?
Alright, that’s it for me, see you on the next episode of Seeker+.