Fun with the nasal cycle

Did you know that most of us have two nostrils? It’s strange — we have a single trachea, but it branches into two pathways up top, and furthermore, those two terminal pathways are elaborate and mazelike, with a network of sinuses and these convoluted turbinate bones taking up much of the space behind your nose. I’d always just chalked it up to a side effect of bilateral symmetry (eh, you know, developmental biologist), but at the very least, it does have physiological consequences. Among those consequences is that there is a nasal cycle. You don’t breathe in equally through both nostrils, there is an alternating rhythm.

Try it yourself right now. Consciously consider what you feel as you breathe in and out normally — you probably can detect that one nostril seems a little bit more open than the other (if you’ve got a cold or allergies, your perception of this phenomenon may be messed up. Sorry. Get better soon.) As I sit here, for instance, I can tell that my right nostril has somewhat freer airflow than my left. It’s not that I’m having any problems breathing through either, it’s a subtle difference, simply a small, barely detectable asymmetry that is unnoticeable except when I’m consciously thinking about my breathing.

MRI scans through a face

The cool thing about it, though, is that it alternates with a cycle length between about half an hour and 8 hours. The mechanism for that is that a portion of your septum and your inferior turbinate are covered with erectile tissue that becomes gradually engorged in response to sustained airflow, and relaxes as airflow is reduced, so your nostrils take turns getting aroused by breathing and then swapping off with each other to relax and recover.

You can measure the nasal cycle in a precise and continuous way with scientific instruments, if you’d like, but there’s also a rough and ready way. This weekend my wife and I drove to a meeting in Glenwood, and then on to Minneapolis, so we had a couple of long drives together, and we were talking about respiratory physiology, as one does, when I explained about this nasal cycle thing, and we decided to measure it. Since we didn’t have access to an electronics lab in the car, we did a subjective estimate: every half hour, we’d just try to be consciously aware of our breathing and report which nostril was doing most of the work. It beats playing Slug Bug, anyway.

So we did a day’s worth of crude measurements. One problem right away was that Mary was a bit congested and stuffed up, which meant the whole day went by with no change for her, which was a bit boring. She did finally detect a shift that evening, so her nasal cycle was estimated to be a bit longer than 8 hours. Another slight problem is that we also took our son and his girlfriend out to lunch, and mid-meal we had to announce “Nostril check!”, which meant we got some funny looks. But that’s OK, I’m used to getting funny looks.

As for me, I’ve gotten over a nasty cold that had been afflicting me for a while, so my face and sinuses and nasal erectile tissue were in fine fettle, and I was able to measure a couple of cycles, which were both about 3 hours in length.

Give it a try yourself. The obvious weaknesses with the way we were doing it is that the observations are personal and subjective, unlike those done with gadgetry that directly measures airflow, and since we were only doing a check every half hour our results were pretty chunky. The interesting thing about it, though, is that this is a rhythm our bodies express throughout your life, and most of us never even notice. It makes one wonder what other sneaky little patterns your organs are doing without your permission or control.

Kahana-Zweig R, Geva-Sagiv M, Weissbrod A, Secundo L, Soroker N, Sobel N. (2016) Measuring and Characterizing the Human Nasal Cycle. PLoS One 11(10):e0162918


  1. says

    those two terminal pathways are elaborate and mazelike, with a network of sinuses and these convoluted turbinate bones taking up much of the space behind your nose.

    I did once wonder if that was all designed to collect snot and bacteria. My family appear to inherit exceptionally badly designed nasal thingums. I nearly died from a sinus infection as a kid. I’m sure god must have put a lesser demon in charge of that bit of design.

  2. says

    When I first started reading this, right side. By the time I got to the end, I noted a shift to the left. Now I’ll be conscious of this all day long!

  3. says

    Huh, never occurred to me that the two nostrils thing is kind of weird. Now I’m thinking what species in the stories I write might work with just one nostril, or three, to say nothing of the ones with none…
    Also I’m not sure if I was supposed to detect nostril switching with every breath but I kind of did. Now I can’t tell–I think it’s my left, but there’s some gunk in there so that kind of gets in the way. I have a garbage nose anyway, wouldn’t be surprised if the default for me is “neither”…

  4. jupitaur says

    An easy way to measure this is to take a post-it note, cut a couple of little slices out of it (about 1/4 inch wide and a couple of inches long), attach one on each side of the nose so it’s disturbed when you breathe out that nostril. You’ll see which nostril is dominant immediately.

    Bonus points because it looks even nerdier than tape on your glasses.

  5. timmyson says

    Are you not worried about aliasing with your sample interval in your expected observed range?

  6. Siobhan says

    so we had a couple of long drives together, and we were talking about respiratory physiology, as one does,


  7. says

    #6: Yes, since this was a subjective estimation. So I didn’t tell my wife what the expected range was.

    I am not pretending this is a good way to measure it. It’s an easy way to measure it poorly.

  8. jupitaur says

    #8 I don’t have a moustache, so I can’t say for certain, but I guess if you flare it out a little? Or make it shorter? Or just tape it to the moustache itself, sort of a moustache extension? Experiment, man!

  9. says


    I have often noticed that most of my breathing is via one nostril. And which one seems to change from time to time.

    It had never occurred to me that it was supposed to work this way.

  10. slithey tove (twas brillig (stevem)) says

    I experience this cycle quite strongly during pollen season. At night, sleeping on left side, the left nostril will clog. rolling over, the left will clear and the right will clog. roll over, repeat. Used to think the snot was draining from upper nostril to lower, and that made no sense as snot was not the issue, merely congestion. The erectile nature of the tissues makes far more sense. *sniffles*

  11. otis says

    Camels have elaborate nostrils that allow them to condense water vapor from their lungs and recycle what is otherwise lost in the respiration of most species…….thanks Knut Schmidt Nielson!

  12. lumipuna says

    Slithey tove: I had the exact same experience. I knew it was about nasal tissue swelling, but had no idea of there being a regular nasal cycle.

    Right now my right nostril is nearly blocked I hadn’t noticed anything unusual. Generally, being somewhat blocked seems to be my usual state.

  13. Ed Seedhouse says

    I remember reading about this many years ago. Just when I’m not sure, well I’m 73 so what can I say?

    Anyway my nostril design seems to be messed up and the right one is apparently designed to collect and solidify mucus and is also bent, so it’s almost always my left nostril that’s dominant. Why doesn’t someone design a really good automatic nose picking machine?

    Also I have dust allergies and many years of oxymetazoline usage has apparently caused a hole in my septum so both nostrils are connected in a way they weren’t meant to be. Don’t ask me how I found this out, but cocaine had nothing to do with it since I’ve never used that stuff.

  14. Jessie Harban says

    I’d check but I’m pretty severely congested so I don’t know if I even have a nasal cycle.

  15. naturalcynic says

    I have also experienced the conspicuous alternating congestion. At first, when getting a cold, one nostril was completely clogged, then both seemed clear and then the other became clogged. As the cold progressed, both became completely clogged. As the symptoms improved, the total alternation came back accompanied with a scrunching sound as one nostril became clogged. It took only a few seconds for one nostril to go from clear to completely clogged, and about the same time for the other to go from clogged to clear. I never timed the period between alternations, but I noticed that it happened several times per day.

  16. trevorn says

    I learned this when I needed to sleep with a respirator with a nasal mask. I expected to lie awake all night with a blocked nose but found one side and then the other clearing at regular intervals just enough to allow me to breathe. Nice to have an explanation.

  17. allonym says

    I learned about this from the British quiz show QI. It was stated that the cycle is 4 hours on average, and that the dominant side correlates with brain function: when on the left, your mathematical/computational focus increases, and when on the right your spatial/linguistic focus gets a boost. Small effect probably, if any, and of course a quiz show doesn’t bother to cite sources. Still, “Quite Interesting” if true.

  18. says

    This function also helps our smell receptors, some odors are quickly noticed by our receptors in the clearer nostril while some smells take longer to bind to receptors so the slower moving nostril keeps the odors near receptors longer giving us a wider range to our sense of smell.

    Many people who are just getting started on CPAP therapy think that they are plugged up when the machine starts pushing air up their nose, in reality it is the first time they are becoming aware that there is a different amount of air going up each of their nostrils.

  19. oliverkurth says

    You could use a pocket mirror or a cell phone, put that under your nose and breathe out. The glass will fog up for each side. But when I try that right now, both sides fog up almost the same, although it *feels* like my right side has better airflow. So that make me skeptical of the subjective approach.

  20. Anders Kehlet says

    Pretty sure I can feel the tissue directly with my tongue. They’re kinda like little balloony things.
    Hadn’t noticed the alternating thing, but my right one is definitely more engorged atm.

  21. octopod says

    Oh wow! I had always just thought this meant my nose was perpetually semi-clogged — I had no idea it was supposed to work that way!

  22. Rich Woods says

    @Ed Seedhouse #17:

    Why doesn’t someone design a really good automatic nose picking machine?

    Someone already has; it’s been around for millennia.

    It’s called a two-year-old.

  23. KG says

    Fun with the nasal cycle

    I tried it, but I found it difficult to get my head down far enough while remaining in the saddle, and when I did, my nose kept getting caught in the chain!

  24. jack16 says

    “Just over a nasty cold”, I notice you seem to get frequent colds. Maybe its an academic affliction? I started taking a vitamin D3 supplement about a dozen years ago. Since then I have had four or five serions colds. I used to say I wasn’t getting colds but then noticed there were fairly frequent times when it felt like I was getting a cold. The next day the symptoms would be gone. So . . . check your vitamin D levels with your blood tests. If its at the low end of the range supplement it. Can’t hurt.