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One of the most frequent questions we get asked  on Journey to the Microcosmos is how James,   our master of microscopes, stays safe  while gathering and studying samples.   After all, as beautiful as the microcosmos is,  there are plenty of parasites and pathogens in   there that we’d prefer to keep under  the microscope and out of our bodies.  But while James has simple and effective  guidelines to protect his health—like   making sure he always washes his hands before and  after handling samples, and never venturing into   a pond with an open wound—there are times  when those measures don’t quite cut it.   These are the times when no matter how much  you protect yourself outside or inside,   the microcosmos gets the best of you. These are the times of the dust mite.  Now we don’t usually start these videos with  a warning, but we’re going to do that today.   While working on this video, at least 4  members of the Journey to the Microcosmos team   found themselves having a bit of a  crisis about how clean their homes were.  If you’ve found yourself sneezing and wheezing and   running around miserable with a runny  nose because of dust, this arachnid   is probably the culprit—though perhaps  not in the way you would expect.  Dust mites are small in the grand scheme of  things, but large in the microcosmos, hitting just   around 300 micrometers in length.

Their bodies are  decked out with four pairs of legs ending in feet   that act like suction cups as they wander in their  quest for three things: water, food, and darkness.  Dust mites love humidity because their  lives depend on it. They don’t drink water   so much as they osmosis it into them, relying on  a salt-filled gland near their mouth to absorb   water vapor from the air around them. So if their  surroundings become more arid, an adult dust mite   will wither away until it eventually dies.

This is a challenge for dust mites that live   in places with seasons, where wet and rainy falls  give way to dry winters. To survive those shifts,   they rely on the resilience of their  younger brethren—the nymphs—whose   forms are able to withstand the lack of moisture. The seasons of the dust mite’s life was one of the   important clues that helped scientists in the 20th  century understand their role in dust allergies.   Scientists identified dust as the source of some  kind of allergen in the 1920s, but they were not   sure what it was exactly about dust that did it.  They just knew that people all over the globe   suffered from dust allergies, and that these  allergies were often seasonal, peaking in the   autumn, particularly after warm, humid summers2.

And other possible sources, like animal dander   or mold, just didn’t quite fit right with the  seasonality of the allergy. But in the 1960s,   scientists in the Netherlands and Japan realized  that the dust mite might be the culprit.   They’re found in large numbers in the dust that  lines the unwashed and untouched corners of our   homes, their populations peaking in time with the  runny noses and bleary eyes of dust allergies.  But while experiments confirmed that mites  really were the source of people’s sensitivities   to house dust, it wasn’t clear what made them  so special. So, we’ll get to that in a bit...  James often finds dust mites in the humidity  chambers he uses to keep his microbes alive.   These chambers are made up of a  dish lined with wet toilet paper,   which is just about all a dust mite needs to feel  right at home—especially when there’s potentially   some delicious microbes to munch on.

So to keep  those other microbes from becoming a mite meal,   James has to regularly clean out  and disinfect the humidity chamber.  Now, that cleaning might get rid of the  dust mites in the humidity chamber, but   the problem is that our houses are full of  food for them because our houses are full of   us—of flakes from our skin that shed and gather  all around and sustain the invisible mite.  And this is a problem not just because it  means the mite can thrive in our homes.   It’s a problem because food means poop. Over  the course of its life, a mite will produce   about 1000 pieces of poop that are roughly the  size of a grain of pollen. Inside those bits of   fecal matter are enzymes that help the dust mite  eat its own poop and get nutrients that it might   not have gotten the first time around.

But should the dust mite choose to not   revisit its prior meals, the feces will float  around the room, attached to other particles   until eventually they settle down—perhaps on  a pillow, or on a pet’s bed, or a car seat.   It’s like we’re living in a gigantic snow globe,  except that the snow... is dust mite feces.  In 1981, researchers confirmed the bad news about  this animal’s poop— people are allergic to it.   To be more specific, they confirmed  that dust mite poop contains specific   proteins that many people are allergic to. So if you’re airing out some sheets and you start   sneezing, what you might actually be reacting  to is dust mite feces flying around the air.  Now, we apologize for this mental image but it  is reality, and it has embedded in our heads,   so we have to share it with you as well. But  we can offer what might be a small comfort:   there is another allergen from dust  mites that has nothing to do with poop.  Dust mites have a fairly lengthy mating process,  sometimes taking up to two days to finish—this   is a pretty lengthy time for any organism, but  especially for an animal that’s only got about   100 total days to live.

Over the course of their  life, the female dust mite will lay up to 80 eggs,   which hatch into larvae that then go through  several different stages of development   before becoming adults With each passing stage,   the dust mite sheds its exoskeleton, leaving  behind its youth. And that exoskeleton provides   some of the other allergens for people react to. But though that is something people are sometimes   allergic to, it really is mostly just the poop  that sets off people’s allergies.

So I guess there   really wasn’t that much comfort there after all. And even for a trained and cautious   microbiologist, dust mites can  become an unwelcome surprise.  Once, James brought home some samples taken from  a water dish that his neighbor left outside for   their cat. The surface was covered in tiny round  things, and James thought they might be rotifers.  But when he looked at the surface of the scum  under the microscope, there were no charming   rotifers to be found.

It was mites, just  hundreds of them crawling around the slide.  It was so unpleasant that James  immediately bleached the slide.  Now, he’s not sure if that sample is the reason,  but for days after, James kept sneezing and   having to deal with a runny nose, all of  which pointed to a potential mite invasion.  Fortunately though, our homes are not a utopia  for dust mites. What they really need is dark,   which is why they prefer to dig themselves deep  into carpets and other soft things that give them   space to burrow4. Dust mites have a harder time  with materials like suede that are difficult to   hide themselves in5, and they usually avoid  hard surfaces that are exposed to light.  So for James, his weapons against  the mite invasion were clear:   a vacuum, a mattress cleaner, and a strong  UV light bulb.

It is one of the more ignoble   ends to one of our organisms. We don’t like  to hurt them, unless they are hurting us.   But I am sure there’s a dust mite somewhere in our  homes right now, settling into a soft, dark abode   of its own, with hardly a care in the world for  the battle that was waged to bring you this video.  Thank you for coming on this journey with us as  we explore the unseen world that surrounds us.  And we would like to thank Blinkist  for sponsoring today’s episode. Blinkist is an app that takes the best insights  and need-to-know information from over 4,000   nonfiction books and condenses them down into  just 15 minutes that you can read or listen to.

Maybe you have an idea for a podcast that you  just haven’t been able to get off the ground yet?   Then we highly recommend checking  out Everybody Has a Podcast   (Except You) by Justin, Travis,  and Griffin McElroy on Blinkist. It’s a funny and inspiring, hands-on guide   to making your own podcast and it will  walk you through everything from choosing   a topic to building an audience and you  can check that out right now on Blinkist. It can be hard to find the time to sit down and  learn, but with Blinkist you can explore their   massive library of books in categories like  self-help, business, science, and history.

And if you’re one of the first 100 people to  sign up today using,   you can get free unlimited access for 7 days  and you’ll also get 25% off if you decide to   get a full membership. Check out the link in  the description to start your free 7-day trial.  It might be that your name is coming up on  the screen right now. And if that is the case,   I just want to say “Thank you!” These  are all the names of our Patreon patrons.   They are the people who make this project possible  and without them, we would not be able to continue   exploring all of the nooks and crannies and ins  and outs of the tiny world that surrounds us.  So, thank you all, to all of our patrons,  and if you would like to become one of them,   you can go to

If you want to see more from our Master   of Microscopes James Weiss, you can check  out Jam and Germs on Instagram or TikTok.   And if you want to see more from us, there’s  always a subscribe button somewhere nearby. There's a tickle in my nose. Oh god!