That clear fluid is healthy mucus, a mishmash of water, proteins, antibodies, and infection-fighting substances. Your body produces about a quart of it a day. Its purpose: to irrigate your nasal passages and trap and clear out dust, pollutants, and allergens.
Mucus that sits around in clogged nasal passages thickens and becomes cloudy as it loses moisture. This is usually just a sign of dehydration. Chug lots of fluid and spritz your nostrils with an OTC saline spray to thin the secretions.
You may have a virus. As infection-nuking cells like white blood cells race to the scene, they get swept up into your mucus. When they die off, they give your snot a pale yellow or brownish tint. Rest, get plenty of fluids and cue up a Netflix binge. You’ll likely feel a bit crummy for the next seven to 10 days; if it lasts longer, see your M.D.
Contrary to popular belief, green goo doesn’t mean you have a bacterial infection. What might: If your discolored snot lasts more than two weeks, and symptoms like facial pressure and congestion are getting worse, not better. Then it’s time to call the doc.
If you’ve been blowing your honker especially hard, or the weather is dry, blood vessels that are close to the surface in your nose can rupture and spill their contents. Use a humidifier at night, and when you go out, wrap a scarf around your nose—both add moisture to the air your nose is sucking in.