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Hank: Alright, it turns out, it isn't just me.  When you get a terrible head cold, like half of your nose gets completely stuffed up, but the other side, you can just like, get like a trickle of air through.  Even stranger, every couple of hours, your nostrils switch places between being mostly stuffed and all stuffed.  Why does your body do this to you? 

Well, actually, your nostrils trade breathing duty all the time, you just notice it more when you're congested.  It's called the Nasal Cycle, and about 8 of every 10 people experience it to some degree.  In people who have a nasal cycle, one nostril is more swollen than the other, restricting the flow of air.  Every four hours or so, the swelling in the first nostril goes down and goes up in the other.  

Now, there are reasons for this, and they have to do with why you have two nostrils in the first place, besides that it's super cute.  Having two nostrils lets them split the workload and makes you a much better smeller.  Let's start with the fact that your nose is the gateway between your lungs and the rest of the world.  Lungs require warm, moist air, no matter how cold it is outside, and your nose warms and humidifies the air you breathe.  But especially when you breathe a lot of dry, cold air, it takes a toll on the lining of your nasal passages.  The little hairs that maintain your respiratory tract, called cilia, work best if they get a break every now and then.  If they don't get a break, they dry out, and if they dry out, they can't keep mucus and airborne particles out of your lungs.  Restricting the amount of air flowing past them gives the cilia a chance to relax. 

The nasal cycle also helps you smell better.  A smell is a detection of free-floating chemicals in the air.  These compounds meet up with receptors in your nose and form temporary chemical bonds with them.  Then the receptors send a signal to your brain, and your brain's like, 'Oh, I smelled something.'  But some odor chemicals bind to your nasal receptors more easily than others.  These stickier smells need to move in faster-flowing air in order for you to detect them, otherwise, they'll just get caught in the entrance to your nose and won't be detected by the receptors toward the back.  By contrast, chemicals that don't stick as easily need a slower air flow, so they have a chance to bind to their receptors before they fly by.  So our noses split the difference, restricting the air flow on one side, and letting it zip through on the other, allowing us to detect a greater range of smells. 

So while it may be inconvenient when you get a cold, the nasal cycle helps keep your lungs in working order, and allows you to appreciate complex smells, like chocolate.  Thank you for asking, now I have a question for you, which one is it for you right now, cause for me, it's this one.  This one's open, and this one's more closed, and if you don't have a nasal cycle, I would also be interested to know that. 

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