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Why Does Only One Nostril Get Congested When I’m Sick?

Imagine only half your dick got an erection at a time — that’s essentially how your sinuses work

Whenever I get sick, it feels like a mucoid military squadron chooses one of my nasal passages to pummel and refuses to let it rest. These snotty squatters are a nasal nuisance, and they only ever seem to flood one side of my sinuses. My nose is not a duplex house! What is going on?

I’m sure this happens to you, too. Because it’s not exactly true that only one nostril is clogged at a time, but it definitely feels like it is, thanks to an alternating nasal cycle. 

“The alternating nasal cycle is a normal neurologic, physiologic cycle where one side of our nasal cavity tissue engorges, gets congested or gets larger every three hours or so,” says Omid Mehdizadeh, an otolaryngologist and laryngologist at Providence Saint John’s Health Center in Santa Monica, California. Basically, “one side gets bigger when the other side gets smaller.” 

According to ScienceAlert, the body inflates tissue with blood into one nostril. And so, it’s like if only half your dick got an erection. Mehdizadeh corroborates this analogy: “What essentially causes congestion and not congestion is increased blood flow. It’s the very small microscopic blood vessels that are neurologically mediated, so they’re either dilating or constricting.” 

So, like a boner in your nose? “I guess just like an erection,” Mehdizadeh says.

The alternating nasal cycle, however, is actually a great thing for your sinuses, even though it feels like it makes your congestion worse. To use another analogy (this one non-dick related), it’s like Drano for the nose, ensuring that one side of the nasal cavity is always being wiped clean of mucus and debris. Mehdizadeh says when we get a cold, the process is exaggerated. There’s simply more mucus to clean, which is, in part, why we begin sniffling as the cold sets in. 

But even if not all mucus is cleaned out in one cycle, we’re still breathing out of both nostrils. “As long as you have the nasal airways open on both sides, even if one side is a little bit more swollen, you’re still breathing out of both sides,” Mehdizadeh says. 

Of course, any nasal trauma — such as a broken nose or deviated septum (watch out for those trendy piercings) — can hinder airflow through the nose or disturb the alternating nasal cycle. The same goes for medical conditions like chronic sinusitis or nasal polyps (noncancerous growths in the nasal passages or sinuses). 

It’s in these instances that we start breathing through our mouth, as anyone with a cat allergy can tell you. But mouth breathing is not physiologic, Mehdizadeh says: The human body was never made to breathe out of the mouth.

“There’s actually receptors inside our nose that are able to detect airflow. There are signals going to our brain, saying we’re breathing well and we’re getting enough oxygen,” Mehdizadeh explains. “From a lung standpoint, we actually get a greater inbreathe — a greater volume of air — psychologically when we breathe through our nose than our mouth.” 

This cycle is also believed to increase our sense of smell. Matt Soniak writes for Mental Floss that certain smells are more easily detected and processed in a fast-moving airstream like a decongested nostril, while other smells are picked up in a slower airstream. “The alternating congestion gives the mucus and cilia (the tiny hairs up in your nose) in each nostril a well-deserved break from the onslaught of air and prevents the insides of your nostrils from drying out, cracking and bleeding,” Soniak outlines.

So maybe next time I have a cold, I’ll be more kind to my nose. It’s just a little depleted and trying to get its groove back. I certainly can relate to that.