So, what causes this common and annoying symptom? When you have a cold or virus, chemicals called histamines increase blood flow to your nose and the tissue lining your nasal passages, according to the American Academy of Otolaryngology. But when this happens, the tissue inside your nose becomes inflamed and swollen, so there's less room for air to get through, and you feel stuffy. On top of that, your nose makes more mucus when you're sick, so it feels even more clogged.
Luckily there are several ways to thin the mucus in your nose and make it easier to breathe, so we've rounded up the strategies and solutions that actually work. In the meantime, just embrace being a mouth-breather, and know that this will eventually pass. (And if your stuffy nose doesn't go away after 10 days, or if you also have a fever in addition to the sniffles, see your doctor.)