Clear: Colorless snot is normal. If you're producing more than usual and it's stringy, you may have allergies. If it's liquidy, you may have a virus.
White: Thick, whitish mucus that lasts more than two weeks and includes sinus pain or a fever may indicate an infection.
Yellow: When white blood cells fight off infections, it makes your snot yellow. The good news: Your body is doing what it should. The bad news: You're probably sick. It may clear on its own, but if not, visit your doctor.
Green: Your white blood cells are working overtime to fight off an infection. If it's been 10-plus days, your doctor may prescribe antibiotics to help the fight.
Red: Pink or red mucus indicates blood, often due to irritated nasal passages. It's common in dry climates and high elevations, and for people with allergies or asthma.
Brown: Heavy air pollution can cause brown mucus. If the air quality is poor, limit your time outdoors. Tobacco use could also be the culprit.
Black: Black mucus may indicate a serious fungal infection or other health issue. Head to your doctor right away.
“Nasal saline rinses are one of the most effective ways to help your body fight against sinus issues and remove excess mucus,” Gellner says.