I’ve been the proud owner of a nose for over thirty-eight years and went through more than thirteen continuous years of medical training. Yet, somehow, news of the nasal cycle had utterly passed me by until I read this article by Sarah Zhang in The Atlantic.

Since I learned about it, I’ve been borderline obsessed with it. I already knew that humans effectively have two noses, like we have two eyes and two ears. Each nostril connects to an independent nasal cavity, a complex construction with multiple functions. These include filtering, warming and humidifying air, as well as containing the olfactory epithelium which allows us to smell (and, to a large extent, taste) things. The nose also plays a vital role in speech.

It was news to me that each of the cavities contains erectile tissue similar to that found in the sex organs. Each side alternatives throughout the day in swelling, leading to slight congestion. This ensures that one cavity always has high airflow and the other low. This is important for the olfactory epithelium because different chemicals take different amounts of time to bind, meaning that we need high and low-flow surfaces simultaneously to have the full spectrum of scent. The cilia, tiny hairs which clear mucus, also suspend their usual pattern of beating on the congested side, allowing it to be more moist and hence help humidify the air we breathe.

Even more astoundingly, when one lies on one’s side, it appears that signals from the compressed armpit can induce the nasal passages on the opposite side to open.

Now that I’ve learned this, it’s obvious: I’ve become obsessed with noting which nostril is congested throughout the day. Wendy and I even sometimes ask each other out of mild amazement that we’ve never noticed.

I trust that you, too, will be amazed by this and will spend the next few days noticing with fascination what your nose is up to.