With autumn officially in full swing and the kids back in school, the coughs, colds and bugs are back with a vengeance.
And, unless you have the immune system of a superhero, the chances are you're going to catch a cold at one point or another over the next few months.
While all aspects of having a cold are pretty rubbish, the most annoying symptom is arguably having a blocked nose, but have you ever noticed that it's always one particular side that feels blocked at once?
Even if you've not really registered it before, it's all down to a little something called the nasal cycle, which most of us had never even heard of until explained by Lorraine and Good Morning Britain resident doctor, Dr. Amir Khan.
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The revelation came at the end of last week, when Lorraine host, Christine Lampard, asked why she always finds one nostril more blocked than the other while having a cold.
In a bid to explain the phenomenon, Dr. Amir asked her and everyone at home to breathe in through their nose.
"You're only breathing through one nostril, think about it," he explained. "The air is only going through one nostril. That is because there is something called the nasal cycle, which means your nostrils take it in shifts to work."
Dr. Amir continued: "So one side, the blood vessels and the tissues swell, and on the other side will be breathing normally, and every two to six hours they will switch shifts.
"And that keeps the nostrils healthy, keeps the air flowing, keeps it nice and moist, and keeps your nostrils filtering that air as well."
If you're sitting there, with your hands under your nostrils trying to determine which nostrils s currently on duty, you're not alone, but it helps to get an understanding of why this actually happens.
Dr. Amir: "When you've got a cold, that still happens but it happens more, so the swelling takes place more so you generally breathe through one nostril.
"If you blow your nose when you've got a cold, you'll notice the mucus only comes out of one side, and then over a few hours it will come out the other side because they'll switch over, so there you go."
After many years of experiencing several colds a year, it's pretty mind-blowing to have finally discovered the secret of our nostrils' work rota. And, after a clip of the chat went up on Instagram, there were lots of people who were equally astonished at the revelation.
"Today I was this old when I learned this. Why is this so mind blowing and fascinating?!" one person commented. "We all sat doing this right? Right nostril on duty currently, I am acutely aware."
A second added: "I am 74 and just learning this. Every night i wake up and one side of my nose is bunged up. Who knew?!"
Emma Rosemurgey